Nango E, Yamamoto T, Kumasaka T, Eguchi T. Crystal structure of 3-isopropylmalate dehydrogenase in complex with NAD(+) and a designed inhibitor.
Bioorg Med Chem 2009;
17:7789-94. [PMID:
19833522 DOI:
10.1016/j.bmc.2009.09.025]
[Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2009] [Revised: 09/12/2009] [Accepted: 09/15/2009] [Indexed: 10/20/2022]
Abstract
Isopropylmalate dehydrogenase (IPMDH) is the third enzyme specific to leucine biosynthesis in microorganisms and plants, and catalyzes the oxidative decarboxylation of (2R,3S)-3-isopropylmalate to alpha-ketoisocaproate using NAD(+) as an oxidizing agent. In this study, a thia-analogue of the substrate was designed and synthesized as an inhibitor for IPMDH. The analogue showed strong competitive inhibitory activity with K(i)=62nM toward IPMDH derived from Thermus thermophilus. Moreover, the crystal structure of T. thermophilus IPMDH in a ternary complex with NAD(+) and the inhibitor has been determined at 2.8A resolution. The inhibitor exists as a decarboxylated product with an enol/enolate form in the active site. The product interacts with Arg 94, Asn 102, Ser 259, Glu 270, and a water molecule hydrogen-bonding with Arg 132. All interactions between the product and the enzyme were observed in the position associated with keto-enol tautomerization. This result implies that the tautomerization step of the thia-analogue during the IPMDH reaction is involved in the inhibition.
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