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Biosynthesis of o-succinylbenzoic acid. II: Properties of o-succinylbenzoic acid synthase, an enzyme involved in vitamin K2 biosynthesis.

The enzyme system (OSB2 synthase) catalyzing the synthesis of o-succinylbenzoic acid from isochorismic acid and alpha-ketoglutaric acid in the presence of thiamine pyrophosphate was isolated from Escherichia coli AN 154 and characterized. The purification factor of the enzyme did not increase during column chromatography on Sephadex G-200 or chromatofocusing, suggesting that the OSB synthase is labile. Chromatography on DEAE-Sephadex A-50 or A-25 showed that an enzyme activity separated from fractions containing OSB synthase that decarboxylates alpha-ketoglutarate. This activity is provisionally referred to as the decarboxylating "subunit" or decarboxylating activity of OSB synthase. Both the "subunit" and the holoenzyme were characterized with respect to pH optimum, temperature optimum, and KM values. The OSB synthase loses all activity during treatment with EDTA and activity is most efficiently restored with Mn2+. The activity of the decarboxylating subunit did not depend on Mn2+. When the decarboxylating fraction was incubated with alpha-ketoglutarate and thiamine pyrophosphate, succinic semialdehyde could be isolated as its hydrazone. After treatment of the incubation mixture with phosphorylase a compound was isolated which is most likely the thiamine adduct of succinic semialdehyde.

Carbon-Carbon Lyases↗

Studies on the biosynthesis of bialaphos (SF-1293) Part 3. Production of phosphinic acid derivatives, MP-103, MP-104 and MP-105, by a blocked mutant of Streptomyces hygroscopicus SF-1293 and their roles in the biosynthesis of bialaphos.

During biosynthetic studies on bialaphos to reveal the formation mechanisms of carbon-phosphorous bonds in detail, three new metabolites containing a H-P-C bond structure were isolated from the fermentation broth of a mutant of Streptomyces hygroscopicus SF-1293. Based on the spectroscopic analysis, the structures of these compounds have been determined as shown in Fig. 1. Transformation experiments of these metabolites to bialaphos suggested that the reduction of the phosphorous atom in phosphate will take place at an early biosynthetic stage.

Biotransformation↗