Physical Properties and Kinetic Behavior of a Cephalosporin Acetylesterase Produced by Bacillus subtilis
AUTOR(ES)
Abbott, Bernard J.
RESUMO
An esterase that deacetylates cephalosporins was recovered from the supernatant of a Bacillus subtilis culture. It was partially purified by ammonium sulfate fractionation and ultrafiltration. The enzyme had a temperature optimum between 40 and 50 C and a pH optimum of 7.0. The molecular weight was estimated by gel filtration to be 190,000. The enzyme was very stable and retained greater than 80% of its activity after storage in solution at 25 C for 1 month. The esterase exhibited Michaelis-Menton kinetics with the substrates 7-aminocephalosporanic acid (7-ACA) and 7-(thiophene-2-acetamido)cephalosporanic acid (cephalothin); the Km values were 2.8 × 10-3 and 8.3 × 10-3 M, respectively. The products of 7-ACA deacetylation were weak competitive inhibitors, and a Ki value of 5.0 × 10-2 M was determined for acetate and of 3.6 × 10-2 M for deacetyl-7-ACA. Weak product inhibition did not prevent the deacetylation reaction from going to completion. A 5-mg/ml solution of partially purified esterase completely hydrolyzed (>99.5%) a 24-mg/ml solution of 7-ACA in 3 h. Because of the kinetic properties and excellent stability, this enzyme may be useful in an immobilized form to prepare large quantities of deacetylated cephalosporin derivatives.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=187196Documentos Relacionados
- Preparation and Properties of a Cephalosporin Acetylesterase Adsorbed onto Bentonite
- Properties of purified sporlets produced by spoII mutants of Bacillus subtilis.
- Physical and kinetic properties of the site specific endonuclease BamHI from Bacillus amyloliquefaciens
- Versatile Properties of a Nonsaturable, Homogeneous Transport System in Bacillus subtilis: Genetic, Kinetic, and Affinity Labeling Studies
- Physical and kinetic properties of the site specific endonuclease Bam HI from Bacillus amylolique-faciens.