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4tsk

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Ketol-acid reductoisomerase from Alicyclobacillus acidocaldarius

Structural highlights

4tsk is a 1 chain structure with sequence from Alicyclobacillus acidocaldarius subsp. acidocaldarius DSM 446. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance.
Method:	X-ray diffraction, Resolution 2.5Å
Ligands:	, ,
Resources:	FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT

Function

ILVC_ALIAD Involved in the biosynthesis of branched-chain amino acids (BCAA). Catalyzes an alkyl-migration followed by a ketol-acid reduction of (S)-2-acetolactate (S2AL) to yield (R)-2,3-dihydroxy-isovalerate. In the isomerase reaction, S2AL is rearranged via a Mg-dependent methyl migration to produce 3-hydroxy-3-methyl-2-ketobutyrate (HMKB). In the reductase reaction, this 2-ketoacid undergoes a metal-dependent reduction by NADPH to yield (R)-2,3-dihydroxy-isovalerate.[HAMAP-Rule:MF_00435]^[1]

Publication Abstract from PubMed

All members of the ketol-acid reductoisomerase (KARI) enzyme family characterized to date have been shown to prefer the nicotinamide adenine dinucleotide phosphate hydride (NADPH) cofactor to nicotinamide adenine dinucleotide hydride (NADH). However, KARIs with the reversed cofactor preference are desirable for industrial applications, including anaerobic fermentation to produce branched-chain amino acids. By applying insights gained from structural and engineering studies of this enzyme family to a comprehensive multiple sequence alignment of KARIs, we identified putative NADH-utilizing KARIs and characterized eight whose catalytic efficiencies using NADH were equal to or greater than NADPH. These are the first naturally NADH-preferring KARIs reported and demonstrate that this property has evolved independently multiple times, using strategies unlike those used previously in the laboratory to engineer a KARI cofactor switch.

Uncovering rare NADH-preferring ketol-acid reductoisomerases.,Brinkmann-Chen S, Cahn JK, Arnold FH Metab Eng. 2014 Aug 27;26C:17-22. doi: 10.1016/j.ymben.2014.08.003. PMID:25172159^[2]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

References

↑ Cahn JK, Brinkmann-Chen S, Spatzal T, Wiig JA, Buller AR, Einsle O, Hu Y, Ribbe MW, Arnold FH. Cofactor specificity motifs and the induced fit mechanism in Class I ketol-acid reductoisomerases. Biochem J. 2015 Apr 7. PMID:25849365 doi:http://dx.doi.org/10.1042/BJ20150183
↑ Brinkmann-Chen S, Cahn JK, Arnold FH. Uncovering rare NADH-preferring ketol-acid reductoisomerases. Metab Eng. 2014 Aug 27;26C:17-22. doi: 10.1016/j.ymben.2014.08.003. PMID:25172159 doi:http://dx.doi.org/10.1016/j.ymben.2014.08.003