Biochemical properties of penicillin amidohydrolase from Micrococcus luteus

Abstract

Some biochemical properties of whole-cell penicillin amidohydrolase from M. luteus have been studied. This whole-cell enzyme showed its maximal activity at 36°C at pH 7.5. It was found that the activation energy of this enzyme was 8.03 kcal (ca. 33.6 kJ) per mol, and this amidohyrolase showed first-order decay at 36°C. The penicillin amidohydrolase was deactivated rapidly at temperatures above 50°C during storage or preincubation for 24 h. The Michaelis constant, K(m), for penicillin G was determined as 2.26 mM, and the substrate inhibition constant, K(is), was 155 mM. The whole-cell penicillin amidohydrolase from M. luteus was capable of hydrolyzing penicillin G, penicillin V, ampicillin, and cephalexin, but not cephalosporin C and cloxacillin. This whole-cell enzyme also had synthetic activity for semisynthetic penicillins or cephalosporins from D-(-)-α-phenylglycine methyl ester and 6-α-aminopenicillanic acid or 7-amino-3-deacetoxycephalosporanic acid.