| 摘要 |
PROBLEM TO BE SOLVED: To obtain a malate dehydrogenase excellent in storage stability and having high specific activity. SOLUTION: This malate dehydrogenase has the following physicochemical properties: (1) action, catalyzing the following reaction: oxalacetic acid + NADH + H<+>←or→L-malic acid + NAD<+> ; (2) substrate specificity, having 2.7×10<-5> M Km to oxalacetic acid; (3) optimum pH and stable pH range, having optimum pH of 8-9 and stable at pH 7-11; (4) molecular weight, 72000 by measurement due to Sephadex G-100gel chromatography; (5) storage stability, having >=95% residual activity after leaving to stand in 100mM tris-hydrochloric acid buffer (pH 9) at ambient temperature (25 deg.C) for 20 days; (6) heat stability, not deactivated by treatment in 100mM tris-hydrochloric acid buffer (pH 9) at 50 deg.C for 15min; (7) specific activity, >=1000U/mg in oxalacetic acid reduction reaction. |
