5YEQ

The structure of Sac-KARI protein

Summary for 5YEQ

• Entry DOI: 10.2210/pdb5yeq/pdb
• Descriptor: Ketol-acid reductoisomerase (NADP(+)), SULFATE ION, MAGNESIUM ION, ... (5 entities in total)
• Functional Keywords: reductase, ahir, nadh, nadph, branched-chain amino acids, bcaa, biofuel, knot domain, metal ion cofactor, acid tolerant enzyme, isomerase
• Biological source: Sulfolobus acidocaldarius
• Total number of polymer chains: 2
• Total formula weight: 78055.95

Authors

Ko, T.P.,Chen, C.Y.,Lin, K.F.,Lin, B.L.,Huang, C.H.,Chiang, C.H.,Horng, J.C.,Tsai, M.D. (deposition date: 2017-09-19, release date: 2018-07-04, Last modification date: 2024-10-23)

Primary citation

Chen, C.Y.,Ko, T.P.,Lin, K.F.,Lin, B.L.,Huang, C.H.,Chiang, C.H.,Horng, J.C.
NADH/NADPH bi-cofactor-utilizing and thermoactive ketol-acid reductoisomerase from Sulfolobus acidocaldarius
Sci Rep, 8:7176-7176, 2018

PubMed Abstract: Ketol-acid reductoisomerase (KARI) is a bifunctional enzyme in the second step of branched-chain amino acids biosynthetic pathway. Most KARIs prefer NADPH as a cofactor. However, KARI with a preference for NADH is desirable in industrial applications including anaerobic fermentation for the production of branched-chain amino acids or biofuels. Here, we characterize a thermoacidophilic archaeal Sac-KARI from Sulfolobus acidocaldarius and present its crystal structure at a 1.75-Å resolution. By comparison with other holo-KARI structures, one sulphate ion is observed in each binding site for the 2'-phosphate of NADPH, implicating its NADPH preference. Sac-KARI has very high affinity for NADPH and NADH, with K values of 0.4 μM for NADPH and 6.0 μM for NADH, suggesting that both are good cofactors at low concentrations although NADPH is favoured over NADH. Furthermore, Sac-KARI can catalyze 2(S)-acetolactate (2S-AL) with either cofactor from 25 to 60 °C, but the enzyme has higher activity by using NADPH. In addition, the catalytic activity of Sac-KARI increases significantly with elevated temperatures and reaches an optimum at 60 °C. Bi-cofactor utilization and the thermoactivity of Sac-KARI make it a potential candidate for use in metabolic engineering or industrial applications under anaerobic or harsh conditions.

PubMed: 29739976
DOI: 10.1038/s41598-018-25361-4

Experimental method

X-RAY DIFFRACTION (1.75 Å)