<b>Recent Progress in Porphyrin and Chlorophyll Biosynthesis</b>

Porra, Robert J.

doi:10.1111/j.1751-1097.1997.tb08596.x

Cited by 130 publications

(87 citation statements)

References 274 publications

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“…The incorporation of 18 O label into these oxygens from 18 O 2 and H 2 18 O during pigment biosynthesis has recently been reviewed [1].…”

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“…Dehydration of [3 1 -hydroxy]-BChl a to [3-vinyl]-BChl a. This dehydration was achieved by heating a dry film of the 3 1 -hydroxy derivative for 30Ϫ40 min at 142°at a reduced pressure using an Edwards Pico-Dry High Vacuum pump operating between 2.5Ϫ1.0 mPa.…”

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confidence: 99%

“…BChl a was reduced in ethanol with 75 mM NaBH 4 : under these conditions, the 13 1 -oxo group of BChl a is not reduced [16]. The [3 1 hydroxy]-BChl a so formed was purified on DEAE-cellulose columns as previously described [6].…”

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Biosynthesis of the 3‐Acetyl and 13¹‐Oxo Groups of Bacteriochlorophyll a in the Facultative Aerobic Bacterium, Rhodovulum sulfidophilum

Porra¹,

Urzinger²,

Winkler³

et al. 1998

European Journal of Biochemistry

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Using 18 O-labelling and mass spectrometry, we have examined bacteriochlorophyll a formation in Rhodovulum sulfidophilum, formerly known as Rhodobacter sulfidophilus, which forms large amounts of BChl a both aerobically in the dark and anaerobically in the light.R. sulfidophilum, growing under strict anaerobiosis in the light, possesses hydratases which incorporate 18 O label from H 2 18 O into both the 13 1 -oxo and 3-acetyl oxygens; in addition, the four carboxyl oxygens at C13 3 and C17 3 were labelled by H2 18 O. Under aerobic conditions in the dark, the labelling of the 13 1 -oxo group by H 2 18 O was reduced indicating that 16 O was being incorporated into this group from air.R. sulfidophilum, grown in the dark under an atmosphere initially containing 50% 18 O2 in Ar, possessed an oxygenase which incorporated 18 O label from 18 O 2 specifically into the 13 1 -oxo group; under these conditions the acetyl and carboxyl groups remained unlabelled.Thus, both an oxygenase and hydratase operate in R. sulfidophilum to form the 13 1 -oxo group of ring E of BChl a; the 3-acetyl group oxygen, however, arises only from water via a hydratase.Keywords : biosynthesis, bacteriochlorophyll a; isocyclic ring E formation ; oxygenase-catalyzed and hydratase-catalyzed cyclization; 3-acetyl formation.Bacteriochlorophyll (BChl) a, an antenna and reaction-centre pigment of many photosynthetic bacteria, possesses six oxygen atoms : in addition to four carboxyl oxygens at C13 3 and C17 3 there are two carbonyl oxygens at C3 1 and C13 1 (see formula in Scheme 1). The incorporation of 18 O label into these oxygens from 18 O 2 and H 2 18 O during pigment biosynthesis has recently been reviewed [1].During BChl a biosynthesis, the first of the two carbonyl groups formed is the 13 1 -oxo group which arises during isocyclic ring E formation from the 13-propionic acid methyl ester side chain of Mg-protoporphyin IX monomethylester: this oxo group is present in all known functional chlorophylls [2].The second carbonyl group is formed several biosynthetic steps later when the 3-acetyl group is formed by enzymic hydration of the 3-vinyl group of chlorophyllide a followed by dehydrogenation [3]. Consistent with this view, the 3-acetyl oxygen of BChl a was derived from water via a hydratase mechanism in both the obligate aerobe, Dedication. This article is dedicated to Prof. Wolfhart Rüdiger on the occasion of his 65th birthday. the facultative photosynthetic bacterium, Rhodobacter sphaeroides, which forms BChl a in both strictly anaerobic conditions in the light and in atmospheres containing up to 6% oxygen in the dark [5].The 13 1 -oxo group of BChl a was also derived from water via a hydratase mechanism in R. sphaeroides [4,6]. In R. denitrificans, however, the 13 1 -oxo group was derived only from molecular oxygen via an oxygenase [4] as also occurs in chlorophyll (Chl) a and Chl b formation in green plants [7Ϫ9] and green algae [10].We have now examined BChl a formation in Rhodovulum sulfidophilum, a purple non-sulphur bacterium and a membe...

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“…The incorporation of 18 O label into these oxygens from 18 O 2 and H 2 18 O during pigment biosynthesis has recently been reviewed [1].…”

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confidence: 99%

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confidence: 99%

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Biosynthesis of the 3‐Acetyl and 13¹‐Oxo Groups of Bacteriochlorophyll a in the Facultative Aerobic Bacterium, Rhodovulum sulfidophilum

Porra¹,

Urzinger²,

Winkler³

et al. 1998

European Journal of Biochemistry

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“…Both end products are required in specific but vastly different amounts and are synthesized within the chloroplast via a common tetrapyrrole biosynthetic pathway (Beale and Weinstein, 1990;Porra, 1997). The branch point for the formation of chlorophyll and heme is the use of Proto by the two enzymes that catalyze metal insertion.…”

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Magnesium-Chelatase from Developing Pea Leaves1

1998

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Mg-chelatase catalyzes the ATP-dependent insertion of Mg 2؉ into protoporphyrin-IX to form Mg-protoporphyrin-IX. This is the first step unique to chlorophyll synthesis, and it lies at the branch point for porphyrin utilization; the other branch leads to heme. Using the stromal fraction of pea (Pisum sativum L. cv Spring) chloroplasts, we have prepared Mg-chelatase in a highly active (1000 pmol 30 min ؊1 mg ؊1 ) and stable form. The reaction had a lag in the time course, which was overcome by preincubation with ATP. The concentration curves for ATP and Mg 2؉ were sigmoidal, with apparent K m values for Mg 2؉ and ATP of 14.3 and 0.35 mM, respectively. The K m for deuteroporphyrin was 8 nM. This K m is 300 times lower than the published porphyrin K m for ferrochelatase. The soluble extract was separated into three fractions by chromatography on blue agarose, followed by size-selective centrifugal ultrafiltration of the column flow-through. All three fractions were required for activity, clearly demonstrating that the plant Mg-chelatase requires at least three protein components. Additionally, only two of the components were required for activation; both were contained in the flow-through from the blue-agarose column.The biosynthesis of heme and chlorophyll are integral parts of chloroplast development and the acquisition of photosynthetic capacity. Both end products are required in specific but vastly different amounts and are synthesized within the chloroplast via a common tetrapyrrole biosynthetic pathway (Beale and Weinstein, 1990;Porra, 1997). The branch point for the formation of chlorophyll and heme is the use of Proto by the two enzymes that catalyze metal insertion. Ferrochelatase catalyzes the insertion of Fe 2ϩ into Proto, whereas Mg-chelatase catalyzes the insertion of Mg 2ϩ into Proto. Because the flux of common precursors to the respective end products is likely to be controlled by modulation of the branch-point enzymes, we were interested in the properties of these enzymes. This report describes the properties of a totally soluble enzyme system from pea (Pisum sativum L. cv Spring) chloroplasts that catalyzes the Mg-chelatase reaction.Previous work has shown that Mg-chelatase activity requires ATP (Pardo et al., 1980; Walker and Weinstein, 1991b). Although the reaction is formally similar to the ferrochelatase reaction, insertion of a divalent cation into Proto, there is no ATP requirement for the Fe-insertion reaction. Our previous work has shown that the Mgchelatase reaction requires at least two different protein components (Walker and Weinstein, 1991b; Walker et al., 1992). We also showed that the reaction proceeds by a two-step mechanism, involving activation followed by Mg 2ϩ insertion; both steps require ATP (Walker and Weinstein, 1994). This hypothesis was based on the following observations. There is a lag phase in the kinetics that can be overcome by preincubation of the crude enzyme fraction with ATP before the porphyrin substrate is added. ATP␥S can substitute for ATP in the preincubatio...

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“…The compounds are regularly and prominently investigated in all known macrocyclic ring systems. [1][2][3][4] Various porphyrins and related molecules are derived from the porphine framework, which contains four pyrrolic subunits linked via four methyne bridges. [2] Excessive production, accumulation, and excretion of porphyrins often result from metabolic aberration.…”

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Analysis of Urinary Porphyrins by High Performance Liquid Chromatography-Electrospray Ionization Mass Spectrometry

Cai

et al. 2011

Journal of Liquid Chromatography & Related Technologies

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Recent Progress in Porphyrin and Chlorophyll Biosynthesis

Cited by 130 publications

References 274 publications

Biosynthesis of the 3‐Acetyl and 13¹‐Oxo Groups of Bacteriochlorophyll a in the Facultative Aerobic Bacterium, Rhodovulum sulfidophilum

Biosynthesis of the 3‐Acetyl and 13¹‐Oxo Groups of Bacteriochlorophyll a in the Facultative Aerobic Bacterium, Rhodovulum sulfidophilum

Magnesium-Chelatase from Developing Pea Leaves1

Analysis of Urinary Porphyrins by High Performance Liquid Chromatography-Electrospray Ionization Mass Spectrometry

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Recent Progress in Porphyrin and Chlorophyll Biosynthesis

Cited by 130 publications

References 274 publications

Biosynthesis of the 3‐Acetyl and 131‐Oxo Groups of Bacteriochlorophyll a in the Facultative Aerobic Bacterium, Rhodovulum sulfidophilum

Biosynthesis of the 3‐Acetyl and 131‐Oxo Groups of Bacteriochlorophyll a in the Facultative Aerobic Bacterium, Rhodovulum sulfidophilum

Magnesium-Chelatase from Developing Pea Leaves1

Analysis of Urinary Porphyrins by High Performance Liquid Chromatography-Electrospray Ionization Mass Spectrometry

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Biosynthesis of the 3‐Acetyl and 13¹‐Oxo Groups of Bacteriochlorophyll a in the Facultative Aerobic Bacterium, Rhodovulum sulfidophilum

Biosynthesis of the 3‐Acetyl and 13¹‐Oxo Groups of Bacteriochlorophyll a in the Facultative Aerobic Bacterium, Rhodovulum sulfidophilum