text: Since the metabolic pathway is conserved across species, the genes are similar too. Extensive studies on the regulation in Saccharomyces cerevisiae have been done. The IMD family of genes and gua1 in yeast correspond to guaB and guaA. Here only IMD genes are guanine sensitive and not gua1 unlike in prokaryotes where the entire operon is sensitive. Mycophenolic acid, a drug which is an inhibitor of IMP dehydrogenase, is an inducer of IMD 2 gene (and hence IMD 2 probably has intrinsic drug activity. Another aspect in which the eukaryotic regulation is very different is that eukaryotes have differential regulation of the branches leading to AMP and GMP. For example, in yeasts AMP synthesis genes are poorly repressed by guanine whereas GMP synthesis genes are not affected by adenine and in humans IMP dehydrogenase synthesis is repressed in the presence of guanosine but not adenosine.