Penicillin acylase-catalyzed ampicillin synthesis using a pH gradient: a new approach to optimization.
The penicillin acylase-catalyzed synthesis of ampicillin by acyl transfer from D-(-)-phenylglycine amide (D-PGA) to 6-aminopenicillanic acid (6-APA) becomes more effective when a judiciously chosen pH gradient is applied in the course of the process. This reaction concept is based on two experimental observations: 1) The ratio of the initial synthesis and hydrolysis rates (V(S)/V(H)) is pH-dependent and exhibits a maximum at pH 6.5-7.0 for a saturated solution of 6-APA; 2) at a fixed 6-APA concentration below saturation, V(S)/V(H) increases with decreasing pH. Optimum synthetic efficiency could, therefore, be achieved by starting with a concentrated 6-APA solution at pH 7 and gradually decreasing the pH to 6.3 in the course of 6-APA consumption. A conversion of 96% of 6-APA and 71% of D-PGA into ampicillin was accomplished in an optimized procedure, which significantly exceeds the efficiency of enzymatic synthesis performed at a constant pH of either 7.0 or 6.3.
Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119899 Moscow, Russia.
Maxim I
MI
Youshko
Luuk M
LM
van Langen
Erik
E
de Vroom
Fred
F
van Rantwijk
Roger A
RA
Sheldon
Vytas K
VK
Svedas
D000667:Ampicillin / Q000138:chemical synthesis* / Q000378:metabolism*; D002384:Catalysis; D002460:Cell Line; D004926:Escherichia coli / Q000201:enzymology*; D005998:Glycine / Q000031:analogs & derivatives* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008956:Models, Chemical; D010397:Penicillanic Acid / Q000031:analogs & derivatives* / Q000378:metabolism*; D010399:Penicillin Amidase / Q000378:metabolism*; D011522:Protons; D011786:Quality Control; D012680:Sensitivity and Specificity
D011522:Protons; C470025:phenylglycinamide; C008852:2-phenylglycine; D000667:Ampicillin; D010397:Penicillanic Acid; D010399:Penicillin Amidase; C004408:aminopenicillanic acid; D005998:Glycine