The physico-chemical properties of the purified glucose isomerases [D-xylose ketol iso merase, EC 5.3.1.51 of Streptomyces olivochromogenes and Bacillus stearothermophilus were examined. The molecular size and shape of both enzymes were similar. The molecular weights, sedimentation coefficients, partial specific volumes, diffusion constants and Stokes' radii of the Streptomyces and Bacillus enzymes were determined to be 120,000 and 130,000, 7.55 S and 9.35 S, 0.725 and 0.736 ml/g, 5.87 >: 10-' and 6.82 x 10-7cm2/sec, and 51 and 53 A,

An a-amylase[ƒ¿-1,4-glucan 4-glucanohydrolase, EC 3.2.1.1.], found in the culture filtrate of a strain of Thermoactinomyces vulgaris, was purified by ammonium sulfate fractionation , and DEAF-cellulose and CM-cellulose chromatographies. The purified enzyme showed a single band on disc gel electrophoresis. The optimum reaction pH and temperature were determined to be around pH 5.0 and 70°C. The isoelectric point was determined to be pH 5.2. The a-amylase was stabilized by Cal+. The a-amylase was found to hydrolyze pullulan to panose. Therefore, the hydrolytic pattern of this enzyme is different from those of pullulanase and isopullulanase. The authors have screened thermophilic acti nomycetes strains for a-amylase production and found that one actinomycetes strain iso lated from a soil sample at 50°C produced a new type of ƒ¿-amylase. The a-amylase had the ability to hydrolyze pullulan and showed different properties from the Thermoactino myces a-amylase reported by M. J. Kuo and P. A. Hartman.1,2) Since no ƒ¿-amylases have been reported to hydrolyze the part of pullulan consisting of maltotriose unit, this enzyme seems to be a new type of a-amylase. The present report describes the procedure of puri fication, some properties, and the pattern of pullulan hydrolysis of this ƒ¿-amylase. MATERIALS AND METHODS Microorganism and culture. A thermophilic acti nomycetes strain showing both ƒ¿-amylase and pullulan hydrolyzing activities was isolated from soil at 50°C.

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Although the electrolytically obtained DPNH was not completely oxidized by usual dehydrogenases or diaphorases, one of the authors noticed that its absqrption band at 340 m,u disappeared completely when it was incubated with the extract of mung been seedlings. The reaction was found to be stimulated by the addition of methylene blue, and the product was identified as DPN. Thus, the reaction resembled that of diaphorase, although it was less specific to the configuration of DPNH. But unlike usual diaphorase, it required a cofactor, which was neither flavins nor metallic ion, but an unidentified acidic substance. General properties of the enzyme and the cofactor are reported in this article.