title: Biochemical properties of penicillin amidohydrolase from Micrococcus luteus.
abstract: Some biochemical properties of whole-cell penicillin amidohydrolase from Micrococcus luteus have been studied. This whole-cell enzyme showed its maximal activity at 36 degrees 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 amidohydrolase showed first-order decay at 36 degrees C. The penicillin amidohydrolase was deactivated rapidly at temperatures above 50 degrees C during storage or preincubation for 24 h. The Michaelis constant, Km, for penicillin G was determined as 2.26 mM, and the substrate inhibition constant, Kis, 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-(--)-alpha-phenylglycine methyl ester and 6-alpha-aminopenicillanic acid or 7-amino-3-deacetoxycephalosporanic acid.
mesh_terms: D000581:Amidohydrolases / Q000378:metabolism*; D002511:Cephalosporins / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008837:Micrococcus / Q000201:enzymology*; D010399:Penicillin Amidase / Q000378:metabolism*; D010400:Penicillin G / Q000378:metabolism; D010406:Penicillins / Q000378:metabolism; D013379:Substrate Specificity; D013696:Temperature
chemical_list: D002511:Cephalosporins; D010406:Penicillins; D000581:Amidohydrolases; D010399:Penicillin Amidase; D010400:Penicillin G