J. Biochem, 1988, Vol. 104, No. 1 57-61
© 1988 Japanese Biochemical Society
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Molecular and Catalytic Properties of Angiotensin Converting Enzyme-I from Bovine Seminal Plasma
Division of Biochemisfry, Indian Veterinary Research Institute Izatnagar, U.P. 243 122, India
1 To whom correspondence should be addressed
Angiotensin converting enzyme [EC 3.4.15.1 [EC] ] was shown to exist in two distinct forms in bovine seminal plasma. The higher molecular weight form of the enzyme (angiotensin convering enzyme I) was purified to homogeneity bySephadex G-200 gel filtration, and DEAE-Sepharose, blue Sepharose, and concanavalin A-Sepharose column chromatography. Final recovery of the enzyme was 9.0. The molecular weight of the enzyme was estimated to be 8 x 1O5 by the gel filtration method. A value of 4.6 x 105 was obtained for the reduced and denatured enzyme by dodecylsulfate polyacrylamide gel electrophoresis. The Stokes' radius, diffusion coefficient, and intrinsic viscosity of the purified enzyme were determined to be 95 Å, 2.3 x 107 cm2 and 6.76 ml/g. The enzyme had a specific activity of 105.12 pmol/min/mg protein for hippurylhistidylleucine. The Km value for hippuryihis tidylleucine was found to be 20mM. Studies with EDTA suggest that metal ions which are tightly bound are required for its activity. The enzyme was inhibited by some heavy metal ions but did not required sulfhydryl groups for its activity. Trypsin treatment of the urea-denatured enzyme produced a catalytically active fragment with an Mr of 30,000. Chemical hydrolysis of the native enzyme did not produce any active fragment.