NEW-TYPE OF HEXAMERIC ORNITHINE CARBAMOYLTRANSFERASE WITH ARGINASE ACTIVITY IN THE CEPHAMYCIN PRODUCERS STREPTOMYCES-CLAVULIGERUS AND NOCARDIA LACTAMDURANS
Jl. Delafuente et al., NEW-TYPE OF HEXAMERIC ORNITHINE CARBAMOYLTRANSFERASE WITH ARGINASE ACTIVITY IN THE CEPHAMYCIN PRODUCERS STREPTOMYCES-CLAVULIGERUS AND NOCARDIA LACTAMDURANS, Biochemical journal, 320, 1996, pp. 173-179
The ornithine carbamoyltransferases (OTCases) from the beta-lactam-pro
ducing actinomycetes Streptomyces clavuligerus and Nocardia lactamdura
ns have been purified to near-homogeneity by delta-N-phosphonoacetylor
nithine-Sepharose 4B affinity chromatography. The S. clavuligerus and
N. lactamdurans OTCase monomers had a molecular mass of 37 kDa. The na
tive OTCases of S. clavuligerus, N. lactamdurans and Streptomyces coel
icolor had molecular masses of 248, 251 and 247 kDa respectively, whic
h correspond to a hexameric structure. The apparent K-m values for orn
ithine and carbamoylphosphate of the S. clavuligerus enzyme were respe
ctively 2.3 and 6.0 mM at pH 8.0. The enzyme showed a reverse activity
on citrulline and used lysine and putrescine as substrates. The hexam
eric complex showed coupled arginase-OTCase activities and was able to
convert arginine into citrulline in a carbamoylphosphate-dependent ma
nner. The requirement for carbamoylphosphate might prevent the arginas
e-OTCase complex from carrying out a futile cycle of arginine biosynth
esis and degradation.