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Biomedical subjects

R Bentley

Publications and source records attributed to R Bentley.

At least 73 records · Page 4Linked to original sources
PubMed1980

Conversion of o-succinylbenzoate to dihydroxynaphthoate by extracts of Micrococcus luteus.

Cell-free extracts were prepared from either freshly grown or spray-dried cells of Micrococcus luteus ATCC 4698 by treatment with deoxyribonuclease and lysozyme. These extracts converted o-succinylbenzoic acid (OSB) to 1,4-dihydroxy-2-naphthoic acid (DHNA) as shown by spectrophotofluorometric and radioactivity assays. The conversion required the presence of ATP, CoA, and Mg2+. By use of [2-14C]OSB, the simultaneous production of the spirodilactone form of OSB was also demonstrated. The two products formed from OSB was also demonstrated. The two products formed from OSB were further characterized by gas chromatography combined with mass spectrometry. The production of the spirodilactone was suppressed by the addition of a preparation of the enzyme DHNA synthase obtained from Mycobacterium phlei. (This enzyme catalyzes the conversion of a CoA derivative of OSB to DHNA.) On mild acid treatment, the M. luteus extracts retained the ability to produce spirodilactone but lost the ability to form DHNA. These results are interpreted to mean that an OSB-CoA derivative is an intermediate in the conversion of OSB to DHNA by M. luteus and that two enzymes are involved, one to form the OSB-CoA derivative and the second to carry out a cyclization reaction.

Deoxyribonucleases↗
PubMed1979

Menaquinone (vitamin K2) biosynthesis: conversion of o-succinylbenzoic acid to 1,4-dihydroxy-2-naphthoic acid by Mycobacterium phlei enzymes.

The coenzyme A (CoA) and adenosine 5'-triphosphate-dependent conversion of o-succinylbenzoic acid (4-[2'-carboxyphenyl]-4-oxobutyric acid) to 1,4-dihydroxy-2-naphthoic acids is an important step in menaquinone (vitamin K2) biosynthesis. Cell-free extracts catalyzing this conversion, obtained from Mycobacterium phlei, were separated into three protein fractions by treatment with protamine sulfate. The second fraction (fraction B) and the supernatant (fraction S) alone did not catalyze dihydroxynaphthoate formation, but did so in combination. All of the results were consistent with the formation of an unstable intermediate, likely an o-succinylbenzoyl-CoA compound, by the action of fraction S. Adenosine 5'-triphosphate was required in this reaction and adenosine 5'-monophosphate was formed. This enzyme activity was termed o-succinylbenzoyl-CoA synthetase: the enzyme showed a marked stability to 0.1 N hydrochloric acid. The presumed o-succinylbenzoyl-CoA derivate was rather unstable; under a variety of conditions, it was converted to a spirodilactone form of o-succinylbenzoate. Fraction B contained an enzyme, termed naphthoate synthase, which converted the o-succinylbenzoyl-CoA derivative to 1,4-dihydroxy-2-naphthoate.

Adenosine Monophosphate↗
PubMed1976

Menaquinone biosynthesis: conversion of o-succinylbenzoic acid to 1,4-dihydroxy-2-naphthoic acid and menaquinones by Escherichia coli extracts.

Two intermediates in the biosynthetic pathway to bacterial menaquinones are o-succinylbenzoic acid and 1,4-dihydroxy-2-naphthoic acid. Cell-free extracts have been prepared from Escherichia coli which catalyze the conversion of labeled o-succinylbenzoic acid to the naphthoic acid and also to menaquinones. The naphthoate synthetase has been partially purified and found to require coenzyme A and ATP. The synthetase has an approximate molecular weight of 45 000. The conversion of o-succinylbenzoic acid to menaquinones is stimulated by the presence of farnesyl pyrophosphate. The major menaquinone produced is then MK-3 with the farnesyl side chain.

Benzoates↗
PubMed1975

Biosynthesis of flaviolin and 5,8-dihydroxy-2,7-dimethoxy-1,4-naphthoquinone.

Tracer experiments indicate a polyketide origin for the production of flaviolin (2,5,7-trihydroxy-1,4-naphthoquinone) by Aspergillus niger and 2,7-dimethoxynaphthazarin (5,8-dihydroxy-2,7-dimethoxy-1,4-naphthoquinone) by Streptomyces no. 12396. With the Streptomycete, a "solid state fermentation" technology was used for the incorporation studies. Radioactivity from shikimic acid was effectively incorporated into flaviolin; this conversion, however, proceeded by way of acetic acid. The latter stages of biosynthesis of 2,7-dimethoxynaphthazarin by the Streptomycete were shown to be as follows: flaviolin leads to mompain leads to 2,7-dimethoxynaphthazarin.

Acetates↗
PubMed1973

Biosynthetic precursors of vitamin K as growth promoters for Bacteroides melaninogenicus.

The growth of a vitamin K-requiring strain of Bacteroides melaninogenicus was promoted by some postulated and proven biosynthetic precursors of bacterial menaquinones, 1,4-dihydroxy-2-naphthoic acid, shikimic acid, chorismic acid, and 4(2'-carboxyphenyl)-4-oxobutyric acid. Growth of the organism with [2',4-(14)C(2)]-4(2'-carboxy phenyl)-4-oxobutyric acid as the vitamin K replacement gave rise to a mixture of radioactive menaquinone-9 and menaquinone-10; the dilution factor for this incorporation was 1.8.

Bacteroides↗