Purification and some properties of a novel racemase, which racemizes 2-oxothiazolidine-4-carboxylic acid and 5-oxoproline, from Flectobacillus sp. strain B-1

Abstract

A novel racemase active toward 2-oxothiazolidine-4-carboxylic acid was purified 310-fold with 5% recovery to near homogeneity from a crude extract of Flectobacillus sp. B-1, which had been isolated as a bacterium being able to assimilate ( S)-2-oxothiazolidine-4-carboxylic acid. The molecular weight was estimated to be 92 000 by gel filtration. The purified preparation migrated as a single band of molecular weight 49 000 upon SDS-polyacrylamide gel electrophoresis. The enzyme exhibited maximum activity at pH 8.0 and 45°C. The enzyme also racemized 5-oxoproline but did not act on proline and 4-hydroxyproline. The enzyme apparently had no coenzyme requirement. The enzyme activity was inhibited to 62–100% by SH-blocking reagents such as HgCl 2, AgNO 3, PCMB, iodoacetamide, N-ethylmaleimide and N-bromosuccinimide.