1968 Volume 63 Issue 5 Pages 661-669
The effects of purine and pyrimidine nucleotides and of the nucleosides on partially purified IMP dehydrogenase [EC 1.2.1.14], XMP aminase [EC 6.3.5.2] and succino-AMP lyase [EC 4.3.2.2] activities of Bacillus subtilis M strain of derepressed cells were studied. IMP dehydrogenase was inhibited strongly by GMP, the end product, and by XMP, the direct product of the reaction under dilute con-centrations of IMP and KC1. When the concentrations of IMP and KC1 were both high, ATP also was a strong inhibitor. The fact that Lineweaver-Burk plot against IMP curved upward in the presence of GMP and XMP and was linear in the absence indicated the enzyme was allosteric. XMP aminase utilized i-glutamine more effectively than ammonium sulfate as the amino donor and its activity was inhibited slightly by several ribonucleotides including GDP, GMP, adenosine, UDP, IDP, AMP and ITP. Succino-AMP lyase activity with succino-AMP as the substrate was inhibited competitively by the product, AMP, and its derivative, ATP.
