Chlorophylls: Analysis in Plant Materials

Smith, James H. C.; Benitez, Allen

doi:10.1007/978-3-642-64961-5_6

Cited by 242 publications

(131 citation statements)

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“…Comparing this mass spectrum with that of the unlabelled pigment (Fig. 1A) indicates the incorporation of six 18 O atoms from H2 18 O per pigment molecule; further, the spectrum was consistent with all six oxygens being highly (85%) enriched. Thus, not only the 3-acetyl and 13 1 -oxo group oxygens but also the four carboxyl oxygens at C13 3 and C17 3 were labelled by H 2…”

Section: Resultsmentioning

confidence: 52%

“…1 B) and 50 h (Fig. 1 A) the principal (MϩH) ϩ ion of the isolated BChl a was at 913.5 m/z indicating the incorporation of one 18 O atom/molecule of pigment. An increase in the proportion of unlabelled BChl a produced after 20 h and 50 h is shown by an increase in the band at 911.5 m/z: analysis showed 80% and 50% enrichment at 20 h and 50 h, respectively, but in the latter case 52% more BChl a was produced.…”

Section: Resultsmentioning

confidence: 95%

“…By 18 O-labelling and mass spectrometry, we have shown that R. sulfidophilum incorporates 18 O label from either H 2 18 O or 18 O 2 into the 13 1 -oxo group. Thus we report an organism possessing both a hydratase and oxygenase system for the biosynthesis of ring E of chlorophylls.…”

mentioning

confidence: 95%

“…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].…”

mentioning

confidence: 99%

“…Assay of BChl a. BChl a was assayed by absorption spectrometry using absorption coefficients (ε) of 42.0 mM Ϫ1 · cm Ϫ1 at 770 nm for methanol [17], 91.0 mM Ϫ1 · cm Ϫ1 at 773 nm for diethylether [18] or 69.0 mM Ϫ1 · cm Ϫ1 at 772 nm for acetone [19].…”

mentioning

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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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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Section: Resultsmentioning

confidence: 52%

Section: Resultsmentioning

confidence: 95%

mentioning

confidence: 95%

“…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].…”

mentioning

confidence: 99%

mentioning

confidence: 99%