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Topic: Tetrapyrrole

In the News (Wed 30 Dec 09)

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Mickey Rourke

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Hugh Jackman

	13th International Congress on Photosynthesis (Site not responding. Last check: 2007-10-20)
		Although these compounds are essential for vital activities, photosynthetic organisms must strictly regulate the biosynthesis of tetrapyrroles, since these compounds and their intermediates are known to act as harmful photosensitizers and/or plastid-derived signals for nuclear gene expression.
		For regulation of this pathway, it is generally considered that several specific isoforms catalyzing particular enzymatic steps control the flow of tetrapyrrole intermediates by differential regulation of gene expression depending on environmental and developmental factors.
		Data presented here clearly showed that based on their expression profiles at the onset of greening, genes involved in tetrapyrrole biosynthesis can be classified into 4 categories, in which genes are coordinately regulated to control the biosynthesis.
	abstracts.co.allenpress.com /pweb/pwc2004/document?ID=43569 (265 words)

	Photochemistry and Photobiology: Chloroplast biogenesis 87: Evidence of resonance excitation energy transfer between ...
		Occurrence of resonance excitation energy transfer between tetrapyrrole donors and Chl a acceptors was evidenced by definite excitation maxima that corresponded to absorbance maxima of the various tetrapyrrole donors.
		The detection of resonance excitation energy transfer between anabolic tetrapyrroles and various Chl a-protein complexes may be blurred by the occurrence of endogenous resonance excitation energy transfers that occur in all healthy thylakoids.
		Because the in situ excitation spectrum of a given tetrapyrrole was recorded at the emission maximum of that tetrapyrrole, the most pronounced excitation maximum in the excitation profile corresponded to that particular tetrapyrrole.
	www.findarticles.com /p/articles/mi_qa3931/is_200308/ai_n9297506/pg_3 (1278 words)

	Alan J. Biel 2002 1685
		The regulation of porphobilinogen levels appears to be mediated by a combination of feedback inhibition of aminolevulinate synthase by hemin and by diverting aminolevulinate from the common tetrapyrrole pathway.
		It was previously demonstrated that increasing the level of ferrochelatase in a strain reduced the specific activity of aminolevulinate synthase in that strain and resulted in lowered carbon flow over the common tetrapyrrole pathway (30).
		C]aminolevulinate was incorporated into tetrapyrroles and that the majority of the aminolevulinate was converted to aminohydroxyvalerate (42, 43).
	www.bionewsonline.com /l/d/alan_j_biel_2002_1685.htm (5921 words)

	Photobiotechnologies (Site not responding. Last check: 2007-10-20)
		Specific effects appear to be related to the position of particular tetrapyrrole in the Chl a biosynthetic chain and its electrostatic properties (Amindari et al, 1995).
		The classification of a modulator as an enhancer, inducer or inhibitor of tetrapyrrole accumulation is then determined from the pattern of tetrapyrrole accumulation in the presence and absence of ALA and modulators.
		Since plant and animal cells share the same tetrapyrrole biosynthetic pathway from ALA to protoporphyrin IX (Proto), it was conjectured that it should be possible to adapt the TDPH phenomenon to the photodynamic control of insects.
	w3.ag.uiuc.edu /NRES/LPPBP/PhotoBio.html (5131 words)

	TP introduction
		"Tetrapyrrole" is a term used widely, but loosely, to refer to a member of a class of compounds whose molecules have four rings of the pyrrole type, generally linked together by single-atom bridges between the alpha positions of the five-membered pyrrole rings.
		Tetrapyrroles and their relatives are of importance in several disciplines.
		In systematic tetrapyrrole nomenclature the beginning and direction of numbering is determined by the rules for systematic substitutive nomenclature.
	www.chem.qmw.ac.uk /iupac/tetrapyrrole/intro.html (1072 words)

	Mats Hansson (Tetrapyrrole group) - Biochemistry, Lund University
		Due to the importance of tetrapyrroles like heme and chlorophyll, it is of interest to understand how they are synthesized.
		The principle of tetrapyrrole induced cell death is very efficient and is at present used with great success within agriculture and cancer therapy.
		The tetrapyrrole intermediate protoporphyrin IX is a very effective photosensitizer.
	www.biokem.lu.se /HanssonMats/HanssonMatsEnglish.htm (616 words)

	Physiology
		Because the electron cloud on the tetrapyrrole ring can be polarized in two different orientations, there are actually two different excited singlet states to which the electrons can be elevated.
		Protoporphyrin IX is also exported from the chloroplast to the mitochondrion, where it is used to produce a high abundance of cytochromes in that organelle.
		Thus, products of the tetrapyrrole are involved in photosynthesis (chlorophylls and cytochromes in the chloroplast), respiration (cytochromes in the mitochondrion) and development (phytochrome).
	www-class.unl.edu /biochem/gp2/physiology/lessons/phys_nc_3.html (473 words)

	Gene Expression Profiling of the Tetrapyrrole Metabolic Pathway in Arabidopsis with a Mini-Array System -- Matsumoto et ... (Site not responding. Last check: 2007-10-20)
		Clustering of genes involved in tetrapyrrole biosynthesis at the onset of greening.
		Development-dependent expression of the genes of tetrapyrrole biosynthesis.
		Papenbrock J, Mock H-P, Kruse E, Grimm B (1999) Expression studies in tetrapyrrole biosynthesis: inverse maxima of magnesium chelatase and ferrochelatase activity during cyclic photoperiods.
	www.plantphysiol.org /cgi/content/full/135/4/2379 (6115 words)

	Question 17.4 (Site not responding. Last check: 2007-10-20)
		The chemical structure of phytochrome is fairly complex and consists of a tetrapyrrole chromophore attached to a protein chain by a thioether linkage.
		the open-chain tetrapyrrole in phytochrome is similar to the tetrapyrrole ring found in the chlorophyll molecule but in chlorophyll it forms a ring structure bound around a Mg atom.
		the thioether linkage between the open-chain tetrapyrrole and the protein implies that sulphur is involved which in turn implicates the amino acid cysteine.
	www.mta.ca /~rthompso/Hopkins2/Chapt17H/quest17,4.html (156 words)

	The Heme and Chlorophyll Biosynthetic Pathways (Site not responding. Last check: 2007-10-20)
		Accumulation of the various tetrapyrrole donors was induced by incubation of green tissues with delta-aminolevulinic acid (ALA) and/or 2,2’-dipyridyl (Rebeiz et al, 1988).
		To monitor the possible occurrence of resonance energy transfer between the accumulated anabolic tetrapyrroles and Chl a-protein complexes, excitation spectra were recorded at 77°K at the respective emission maxima of the selected Chl a acceptors, namely at ~685, ~695, and ~735nm.
		Assignment of in situ excitation maxima to various metabolic tetrapyrroles was unambiguous except for a few cases at the short wavelength and long wavelength extremes of excitation bands.
	w3.aces.uiuc.edu /NRES/LPPBP/PathW.html (3829 words)

	Welcome to the School of Biological Sciences (Site not responding. Last check: 2007-10-20)
		Research is focussed on the structure and mechanism of action of enzymes with specific interests in enzymes of haem biosynthesis, polyketide synthases and viral and snake venom proteases.
		Two polymerase enzymes are the subject of detailed investigations: porphobilinogen deaminase that assembles a tetrapyrrole in the haem biosynthesis pathway and 6-methylsalicylic acid synthase that builds the tetraketide precursor for the antibiotic patulin.
		Research on the enzymes involved in the biosynthesis of haem and chlorophyll and other tetrapyrroles has spanned a number of years with recent emphasis being placed on determining the three-dimensional structure of enzymes involved in the initial stages of the pathway.
	www.sbs.soton.ac.uk /staff/pmsj/pmsj.htm (2624 words)

	eMedicine - Diseases of Tetrapyrrole Metabolism: Refsum Disease and the Hepatic Porphyrias : Article by Norman C ... (Site not responding. Last check: 2007-10-20)
		Diseases of Tetrapyrrole Metabolism: Refsum Disease and the Hepatic Porphyrias
		In the diseases of tetrapyrrole metabolism, the value of DNA analysis will not be first-order identification but rather the clarification of new mutations.
		Tetrapyrrole molecules are large-ringed structures developed from 4 pyrrole groups and used in energy metabolism in both plants and animals.
	www.emedicine.com /neuro/topic633.htm (4690 words)

	2002 LSU-HHMI Summer Undergraduate Research Program
		It was previously demonstrated that oxygen regulates the intracellular levels of porphobilinogen, the first intermediate committed to tetrapyrrole biosynthesis.
		It was suggested that regulation of porphobilinogen levels was accomplished by a combination of feedback inhibition of aminolevulinate synthase and diversion of aminolevulinate from the common tetrapyrrole pathway by aminolevulinate dehydrogenase.
		This suggests that oxygen-mediated regulation of the common tetrapyrrole pathway can be altered by increasing the intracellular level of aminolevulinate, and indicates that this is the major step at which carbon-flow over this pathway is regulated.
	www.biology.lsu.edu /hhmiprog/2002/eBaldwin.html (318 words)

	The Biosynthesis of the Tetrapyrrole Pigments - No. 180 And The Mineral Palace by Heidi Julavits, ISBN 0425179826
		The Biosynthesis of the Tetrapyrrole Pigments Chairman: Duilio Arigoni 1994 Arguably the most important pigments of life are the chlorophylls, the light energy-harvesting green pigments of plants and algae, and haem, which forms the non-protein part of haemoglobin, myoglobin and cytochrome c.
		These, and related crucial molecules such as vitamin B¹² and the protoporphyrin IX unit of the cytochromes, are all members of the family of tetrapyrrole pigments sharing many biosynthetic steps and owing their origin to the amino acid pool.
		The biosynthesis of open-chain tetrapyrroles in plants, algae and cyanobacteria is also outlined.
	www.mylfrog.com /biosynthesis.htm (372 words)

	Charlotte Russell
		Heme is a tetrapyrrole which is bound to iron and which is the prosthetic group of the hemoglobins, cytochromes, catalase and peroxidases.
		Other tetrapyrroles found in nature include chlorophylls (tetrapyrrole bound to magnesium), Vitamin B12 (tetrapyrrole bound to cobalt) and Factor 430 (tetrapyrrole bound to nickel).
		We showed that the first committed intermediate in tetrapyrrole biosynthesis, 5-aminolevulinic acid (ALA), is made from glutamate (C5 pathway) in E. coli.
	www.sci.ccny.cuny.edu /chemistry/faculty/russell.html (713 words)

	Matthew Terry - Research
		The chlorophyll (tetrapyrrole) biosynthesis pathway is regulated by light via the phytochrome and cryptochrome families of photoreceptors and by signals from the plastid indicating the developmental status of this organelle.
		The phytochrome family of photoreceptors are dimeric chromoproteins comprised of two 120 kDa apoproteins each covalently bound to a linear tetrapyrrole chromophore, phytochromobilin, which is synthesized from heme in the plastid.
		we are currently investigating the effects of inhibiting phytochromobilin synthesis on regulation of the tetrapyrrole synthesis pathway and plastid development using the aurea and yellow-green-2 mutants of tomato.
	www.soton.ac.uk /~mjt (479 words)

	Regulation of Tetrapyrrole Synthesis in Rhodobacter capsulatus: (Site not responding. Last check: 2007-10-20)
		Tetrapyrroles are biomolecules that serve to bind metal atoms needed for diverse biological functions.
		The tetrapyrrole “skeleton” is synthesized by enzymes encoded by seven
		The PufQ protein appears to coordinate increased tetrapyrrole synthesis (to accommodate increased demand for Bchl) with the synthesis of the apoproteins which bind this tetrapyrrole cofactor.
	sunflower.bio.indiana.edu /~cbauer/research/Jameswebpage.htm (187 words)

	Porphyrin inhibition of rogue prions
		Tetrapyrroles also inhibited PrP-res formation in a cell-free reaction composed predominantly of hamster PrP-res and PrP-sen. Inhibitors were found among phthalocyanines, deuteroporphyrins IX, and meso-substituted porphines; examples included compounds containing anionic, neutral protic, and cationic peripheral substituents and various metals.
		These tetrapyrroles bear some structural resemblance to Congo red in that they all contain hydrophobic aromatic rings and can be synthesized with sulfonate groups.
		Tetrapyrroles can bind strongly and selectively to proteins and affect changes in protein conformation (11-18), potentially critical properties of an effective inhibitor.
	www.mad-cow.org /porphyrin.html (5877 words)

	eMedicine - Diseases of Tetrapyrrole Metabolism: Refsum Disease and the Hepatic Porphyrias : Article Excerpt by: Norman ... (Site not responding. Last check: 2007-10-20)
		Excerpt from Diseases of Tetrapyrrole Metabolism: Refsum Disease and the Hepatic Porphyrias
		Background: Refsum disease (RD) and the hepatic porphyrias are rare inherited neurodegenerative conditions with exacerbations and remissions due to abnormal metabolism of large tetrapyrrole molecules.
		Two common examples of large tetrapyrrole molecules are chlorophyll a, the photosynthetic pigment of green plants, and heme, the prosthetic group of hemoglobin (see Picture 1).
	www.emedicine.com /neuro/byname/diseases-of-tetrapyrrole-metabolism--refsum-disease-and-the-hepatic-porphyrias.htm (632 words)

	Oxygen-Mediated Regulation of Porphobilinogen Formation in Rhodobacter capsulatus -- Biel et al. 184 (6): 1685 -- The ... (Site not responding. Last check: 2007-10-20)
		aminolevulinate is diverted from the common tetrapyrrole pathway.
		common tetrapyrrole pathway is not the synthesis of aminolevulinate.
		which the common tetrapyrrole pathway is regulated (5).
	jb.asm.org /cgi/content/full/184/6/1685 (4355 words)

	TspO of Rhodobacter sphaeroides. A STRUCTURAL AND FUNCTIONAL MODEL FOR THE MAMMALIAN PERIPHERAL BENZODIAZEPINE RECEPTOR ... (Site not responding. Last check: 2007-10-20)
		of an intermediate(s) in the tetrapyrrole biosynthesis pathway.
		Accumulation of Tetrapyrroles by Wild Type and Mutant R. sphaeroides Cells-- We have recently demonstrated that resting cell suspensions of aerobically grown R.
		Analysis of the accumulation of tetrapyrrole pigments from exogenous ALA by wild type and mutant resting cell suspension of
	www.jbc.org /cgi/content/full/275/8/5657 (6738 words)

	Studies on the Specificity of the Tetrapyrrole Substrate for Human Biliverdin-IXalpha Reductase and Biliverdin-IXbeta ... (Site not responding. Last check: 2007-10-20)
		Studies on the Specificity of the Tetrapyrrole Substrate for Human Biliverdin-IXalpha Reductase and Biliverdin-IXbeta Reductase.
		The formation of linear tetrapyrroles by heme catabolism in mammals has, until recently, been discussed in terms of the IX isomers of biliverdin and bilirubin as both heme oxygenases I
		It is conceivable that linear tetrapyrroles may play significant biological roles in mammals, both as antioxidants and as
	www.jbc.org /cgi/content/full/275/25/19009 (4137 words)

	Medicum Net \| Encyclopedia \| Medical Definitions \| Definition of tetrapyrrole
		Tetrapyrrole biosynthesis and its regulation (Microbial and molecular biology series)
		Optical Properties and Structure of Tetrapyrroles: Proceedings of a Symposium Held at the University of Konstanz, West Germany, August 12 to 17, 198
		Optical properties and structure of tetrapyrroles: Proceedings of a symposium held at the University of Konstanz, West Germany, August 12-17, 1984
	medicum.net /dictionary-Medical_Definitions-definition139297-tetrapyrrole... (254 words)

	Harry A (Site not responding. Last check: 2007-10-20)
		Since several comprehensive reviews of tetrapyrrole biosynthesis are available [1-3], this mini-review will concentrate on more recent discoveries and in particular on the terminal enzyme of the pathway ferrochelatase.
		Since the major structural distinction between the N-alkylporphyrins and Porphyrins is that the alkylated ring of the tetrapyrrole is bent about 30û out of the plane of the porphyrin ring (which is otherwise planar), it has been suggested that this bent-ring porphyrin serves as a transition state analog for ferrochelatase.
		Leeper FJ (1994) In: The biosynthesis of the tetrapyrrole pigments.
	www.bmolchem.wisc.edu /teachinglab/fall675/pjkdailey.html (4186 words)

	[No title] (Site not responding. Last check: 2007-10-20)
		The tetrapyrrole cofactors support life systems through their essential catalytic functions; Heme (oxidative metabolism and oxygen transport), Chlorophyll (photosynthesis), Siroheme (sulfite and nitrite assimilation), Cobalamin (vitamin B12 - methionine synthesis and methylmalonyl CoA synthesis) and coenzyme F430 (Methane production).
		Their biosynthesis is complicated and requires anywhere from seven to 30 enzymatic reactions involving a variety of catalytic activities including decarboxylation, methylation, metal ion chelation and porphyrin ring oxidation.
		The Hill lab has successfully determined the structure of several tetrapyrrole biosynthetic enzymes such as human uroporphyrinogen III synthase (U3S), human uroporphyrinogen decarboxylase (UroD) and S. cervisiae siroheme synthase (Met8p).
	www.biochem.utah.edu /~heidi/Tetrapyrrole_Biosynthesis.html (123 words)

	2.6 Structural studies of enzymes involved in Vitamin B12 biosynthesis
		Many critical biochemical processes are carried out with the assistance of tetrapyrrole cofactors such as haem (respiration), vitamin B12 (methionine synthesis), chlorophyll (photosynthesis), sirohaem (nitrite and sulphite reduction) and coenzyme F
		After the initial synthesis of the first tetrapyrrolic intermediate the only additional reaction the cofactors share is that of metal ion chelation.
		Sirohaem is a modified tetrapyrrole that is structurally related to haem, chlorophyll and cobalamin and is the prosthetic group required in the six-electron reduction of both sulphite and nitrite.
	www.ysbl.york.ac.uk /projects/2/2.6.htm (861 words)

	[No title] (Site not responding. Last check: 2007-10-20)
		We observed hy1gon4 to be semi-albino plants, and hy1gun5 albino lethal, in a high-light-sensitive manner.
		Their degree of 'genome uncoupling' (Lhcb expression in the absence of functional chloroplasts) was similar to that observed in single mutants.
		We speculate that either one tetrapyrrole intermediate, which can accumulate anomalously in hy1, or an altered ratio between two intermediates, plays a role as a repressor of Lhcb expression.
	personal.rhul.ac.uk /uhba/047/x2000vinti_plaj.html (302 words)

	Tetrapyrrole Discussion Group - Home Page
		So we now have an Albert Neuberger Lecture in Tetrapyrrole Science to be given on distinguished work in any aspect of this field: the Lecture is expected to be given every two years or so at meetings of the TPDG.
		In a completely different direction, the traces of tetrapyrroles in the geosphere, while challenging the sensitivity of current instrumentation, offer a fascinating way of probing the fate of biological material through geological time periods, as well as offering a method of geochemical oil prospecting.
		t seems to us that the central role of tetrapyrroles in energy transfer processes in living things means that interest in them is bound to be maintained well into the twenty first century.
	www.bmb.leeds.ac.uk /tpdg/history.htm (1217 words)

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