Identification and Characterization of Enzymes Catalyzing Early Steps in Miharamycin and Amipurimycin Biosynthesis.

The biochemical elucidation of the early biosynthetic pathways of miharamycins and amipurimycin revealed the roles of several enzymes, which include GMP hydrolase, represented by MihD/ApmD, and hypothetical proteins, MihI/ApmI, unexpectedly exhibiting the dual function of the guanylglucuronic acid assembly and GMP cleavage. In addition, MihE, a carbonyl reductase that functions on the C2 branch of high-carbon sugars, and MihF, a rare guanine O-methyltransferase, were also functionally verified.