When IMP is the variable substrate, IMP dehydrogenase (EC 1.2.1.14) gives non-linear Lineweaver–Burk plots in the presence of GMP. At 0.1mm-GMP the Hill coefficient n=1.15 and at 0.2mm-GMP n=1.34. In the absence of GMP n=1.0. The fact that n exceeds 1.0 in the presence of GMP indicates that the enzyme possesses regulatory (allosteric) properties. The inhibition by GMP is competitive with respect to IMP and non-competitive with respect to NAD+.

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