The conjugate (10S,11S) JH diol phosphate is the product of a two-step enzymatic process: conversion of JH to JH diol and then addition of a phosphate group to C10. The enzyme responsible for the phosphorylation of JH diol is JH diol kinase (JHDK), which was first characterized from the Malpighian tubules of early fifth instars of M. sexta. JHDK (EC 2.1.7.3) was discovered when an analysis of JH I metabolites in vivo yielded, in addition to the expected metabolites, a very polar JH I conjugate that was subsequently identified as JH I diol phosphate. Maxwell et al. showed JHDK to contain 3 potential calcium binding sites, and a single ATP-Mg2+ binding site (p-loop). The modeled structure contains nine helices, one beta sheet, and 10 loops. JHDK is also present in the silkworm, where it also