The Mycobacterium tuberculosis gene Rv2747 encodes a novel 19-kDa ArgA that catalyzes the initial step in L-arginine biosynthesis, namely the conversion of L-glutamate to α-N-acetyl-L-glutamate. Initial velocity studies reveal that Rv2747 proceeds through a sequential kinetic mechanism, with Km values of 280 mM for L-glutamine and 150 μM for acetyl-coenzyme A and with a kcat value of 200 min-1. Initial velocity studies with L-glutamate showed that even at concentrations of 600 mM, saturation was not observed. Therefore, only a kcat/Km value of 125 M -1 min-1 can be calculated. Inhibition studies reveal that the enzyme is strongly regulated by L-arginine, the end product of the pathway (50% inhibitory concentration, 26 μM). The enzyme was completely inhibited by 500 μM arginine, with a Hill coefficient of 0.60, indicating negatively cooperative binding of L-arginine.
ASJC Scopus subject areas
- Molecular Biology