Biosynthesis of the natural porphyrins: experiments on the ring-closure steps and with the hydroxy-analogue of porphobilinogen

Battersby, Alan R.; Fookes, Christopher J. R.; Matcham, George W. J.; McDonald, Edward; Gustafson-Potter, Kerstin E.

doi:10.1039/c39790000316

Cited by 60 publications

(39 citation statements)

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“…Since the first reports [6,7] on the structure and role of preuroporphyrinogen (2) the Cambridge group has repeated several of our key experiments using our approach but with enzyme preparations from Euglena gvacilis [20] and has subsequently come to similar conclusions to those put forward in our original hypothesis.…”

Section: Acknowledgementsupporting

confidence: 53%

Preuroporphyrinogen, a universal intermediate in the biosynthesis of uroporphyrinogen III

Jordan

Berry

1980

FEBS Letters

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Section: Acknowledgementsupporting

confidence: 53%

Preuroporphyrinogen, a universal intermediate in the biosynthesis of uroporphyrinogen III

Jordan

Berry

1980

FEBS Letters

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“…Interconversion is likely to proceed via hydrolytic cleavage at the terminal pyrrole unit. This process is expected to generate a hydroxy analogue of PBG (denoted S' in Scheme 3 ) , a compound that is known to be a good substrate for HMBS [25]. With respect to our experimental set-up, however, it must be emphasised that in the absence of substrate, the complexes are stable at room temperature on MonoQ, at least during the time needed for chromatography (25 min), as illustrated by the nearly symmetrical peak shapes observed (Fig.…”

Section: Pre-steady-state Kinetic Analysis Of Imrnohilised Hmbs At Lomentioning

confidence: 99%

A Kinetic Analysis of the Reaction Catalysed by (Hydroxymethyl)bilane Synthase

Niemann

Hädener

Matzinger

1994

Helvetica Chimica Acta

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(Hydroxymethy1)bilane synthase (HMBS) catalyses the conversion of porphobilinogen (2) into the (hydroxymethy1)bilane derivative 3, a linear tetrapyrrolic intermediate in the biosynthesis of haem, chlorophyll, and related pigments. The conversion involves the sequential formation of four intermediate covalent enzyme-substrate complexes, before the product is released. We analysed the pre-steady-state kinetics of the formation of the complexes, taking advantage of their remarkable chemical stability allowing chromatographic separation. The experimental approach involved the generation of the complexes while HMBS was immobilised on an anion-exchange column. A solution being 0.2 K,,, in substrate was pumped through the column during a time interval which was varied to sample the pre-steady-state period. Then, the enzyme and enzyme-substrate complexes were eluted and their proportions evaluated. A computer simulation of the pre-steady-state time course, in combination with a x 2 fitting to the experimental data, allowed the specificity constants k,,JK, for the individual steps of the process to be derived. By repeating the analysis with variants of HMBS in which specific amino acids were replaced by others, we demonstrated that it is possible to trace the consequences of amino-acid replacements down to the individual steps of the reaction sequence. Since the positions of the amino acids concerned in the three-dimensional structure were known, detailed structure-function relationships become evident in this way.Introduction. -(Hydroxymethy1)bilane synthase (HMBS, EC 4.3.1.8, also known as porphobilinogen deaminase) is an enzyme of the biosynthetic pathway leading to haem, chlorophyll, vitamin B,,, coenzyme F430, and related tetrapyrrolic pigments. It catalyses the conversion of four equivalents of porphobilinogen (PBG; 2) into (hydroxymethy1)-bilane derivative 3 and ammonia [ 11 [2] (Scheme I ) .HMBS is an enzyme converting PBG into products obeying Michaelis-Menten kinetics (k,,, = 0.1 s-', K,,, = 5-10 ~L M at pH 7.4 for HMBS from Escherichia coli [3]) [4] and displaying chemical reactivity of a polymerase [S]. The signal to stop polymerisation does not require any external factors, but is built into the HMBS molecule itself as soon as four substrate molecules have been processed, the tetrameric product is released. To accomplish the assembly of the bilane, HMBS uses a unique dipyrrin ( = dipyrromethane) cofactor to which the growing chain remains covalently attached [6] [7] (see Scheme 2). The cofactor is in turn covalently bound to the enzyme via the S-atom of a cysteine residue (Cys-242 of the enzyme from E.coli). The HMBS apoenzyme, lacking the cofactor, is capable of assembling its own cofactor from two substrate molecules. Being derived from PBG (2), the cofactor can be isotopically labelled by

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“…Aminomethyl bilane also acted as a substrate for the enzyme but was converted by HmbS at a much lower rate (108)(109)(110). HmbS is evidently able to deaminate the aminomethyl bilane and convert it to HMB (111). The identification of HMB as the product of HmbS and the substrate for UroS then permitted more detailed analyses of the mechanism for the two enzymes.…”

Section: Dailey Et Almentioning

confidence: 99%

Prokaryotic Heme Biosynthesis: Multiple Pathways to a Common Essential Product

Dailey

Gerdes³

et al. 2017

Microbiol Mol Biol Rev

246

329

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SUMMARY The advent of heme during evolution allowed organisms possessing this compound to safely and efficiently carry out a variety of chemical reactions that otherwise were difficult or impossible. While it was long assumed that a single heme biosynthetic pathway existed in nature, over the past decade, it has become clear that there are three distinct pathways among prokaryotes, although all three pathways utilize a common initial core of three enzymes to produce the intermediate uroporphyrinogen III. The most ancient pathway and the only one found in the Archaea converts siroheme to protoheme via an oxygen-independent four-enzyme-step process. Bacteria utilize the initial core pathway but then add one additional common step to produce coproporphyrinogen III. Following this step, Gram-positive organisms oxidize coproporphyrinogen III to coproporphyrin III, insert iron to make coproheme, and finally decarboxylate coproheme to protoheme, whereas Gram-negative bacteria first decarboxylate coproporphyrinogen III to protoporphyrinogen IX and then oxidize this to protoporphyrin IX prior to metal insertion to make protoheme. In order to adapt to oxygen-deficient conditions, two steps in the bacterial pathways have multiple forms to accommodate oxidative reactions in an anaerobic environment. The regulation of these pathways reflects the diversity of bacterial metabolism. This diversity, along with the late recognition that three pathways exist, has significantly slowed advances in this field such that no single organism's heme synthesis pathway regulation is currently completely characterized.

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Biosynthesis of the natural porphyrins: experiments on the ring-closure steps and with the hydroxy-analogue of porphobilinogen

Cited by 60 publications

References 0 publications

Preuroporphyrinogen, a universal intermediate in the biosynthesis of uroporphyrinogen III

Preuroporphyrinogen, a universal intermediate in the biosynthesis of uroporphyrinogen III

A Kinetic Analysis of the Reaction Catalysed by (Hydroxymethyl)bilane Synthase

Prokaryotic Heme Biosynthesis: Multiple Pathways to a Common Essential Product

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