Volume 271, Number 47,
Issue of November 22, 1996
pp. 30256-30262
©1996 by The American Society for Biochemistry and Molecular Biology, Inc.
An Alkaline D-Stereospecific Endopeptidase with
-Lactamase Activity from Bacillus cereus
(Received for publication, July 22, 1996, and in revised form, August 24, 1996)
Yasuhisa
Asano
,
Hajime
Ito
,
Tohru
Dairi
and
Yasuo
Kato
From the Biotechnology Research Center, Toyama Prefectural
University, 5180 Kurokawa, Kosugi, Toyama 939-03, Japan
We purified a novel extracellular
D-stereospecific endopeptidase, alkaline
D-peptidase (D-stereospecific peptide
hydrolase, EC 3.4.11.-), to homogeneity from the culture broth of the
soil bacterium Bacillus cereus strain DF4-B. The
Mr of the enzyme was 37,952, and it was
composed of a single polypeptide chain. The optimal pH for activity was
~10.3. The enzyme was strictly D-stereospecific toward
oligopeptides composed of Dphenylalanine such as
(D-Phe)3 and (D-Phe)4.
The enzyme also acted to a lesser extent on
(D-Phe)6, Boc-(D-Phe)4
(where Boc is tert-butoxycarbonyl),
Boc-(D-Phe)4 methyl ester,
Boc-(D-Phe)3 methyl ester,
Boc-(D-Phe)2, (D-Phe)2, and others, but not upon their corresponding peptides composed of
L-Phe, (D-Ala)n (n = 2-5), (D-Val)3, and
(D-Leu)2. The mode of action of the enzyme was
clarified with synthetic substrates
((D-Phe)2-D-Tyr and
D-Tyr-(D-Phe)2) and eight
stereoisomers of (Phe)3. The enzyme had
-lactamase
activity toward ampicillin and penicillin G, although carboxypeptidase
DD and D-aminopeptidase activities were undetectable.
The gene coding for alkaline D-peptidase (adp)
was cloned into plasmid pUC118, and a 1164-base pair open reading frame
consisting of 388 codons was identified as the adp gene.
The predicted polypeptide was similar to carboxypeptidase DD from
Streptomyces R61, penicillin-binding proteins from
Streptomyces lactamdurans and Bacillus
subtilis, and class C
-lactamases. Thus, the enzyme was
categorized as a new "penicillin-recognizing enzyme."