Creative Enzymes is proud to provide enzyme activity measurement for various enzymes, especially for ketol-acid reductoisomerase (NADP⁺). Our research professionals have always been devoted into providing excellent service and accurate results to our customers.

Ketol-acid reductoisomerase (NADP⁺) (EC 1.1.1.86; KARI), found in many bacteria and archaea, is a member of the oxidoreductase family, and the systematic name of this enzyme class is (R)-2,3-dihydroxy-3-methylbutanoate:NADP+ oxidoreductase (isomerizing). The enzyme can also be called as:

• dihydroxyisovalerate dehydrogenase (isomerizing);
• acetohydroxy acid isomeroreductase;
• ketol acid reductoisomerase;
• alpha-keto-beta-hydroxylacyl reductoisomerase;
• 2-hydroxy-3-keto acid reductoisomerase;
• acetohydroxy acid reductoisomerase;
• acetolactate reductoisomerase;
• dihydroxyisovalerate (isomerizing) dehydrogenase;
• isomeroreductase;
• reductoisomerase;
• ketol-acid reductoisomerase.

Ketol-acid reductoisomerase (NADP⁺) is a bi-functional enzyme that catalyzes two quite different but sequential reactions at one common active site, acting both as an isomerase and a reductase. In the isomerization reaction, 2-hydroxy-2-methyl-3-ketobutyrate (also known as 2-acetolactate) is rearranged to produce 3-hydroxy-3-methyl-2-ketobutyrate, using an Mg²⁺-dependent methyl migration. In the reduction reaction, this 2-ketoacid undergoes an M²⁺-dependent (Mg²⁺, Mn²⁺ or Co²⁺) reduction using NADPH to yield 2,3-dihydroxy-3-methylbutyrate, which is the precursor of valine and leucine. Isoleucine, a third branched-chain amino acid (BCAA), is produced in a pathway that parallels that of valine, using the same series of enzymes, with ketol-acid reductoisomerase (NADP⁺) catalyzing the conversation between 2-hydroxy-2-ethyl-3-ketobutyrate and 2,3-dihydroxy-3-ethylbutyrate. Note that all members of the ketol-acid reductoisomerase enzyme family have been shown to have the preference of nicotinamide adenine dinucleotide phosphate hydride (NADPH) to nicotinamide adenine dinucleotide hydride (NADH) as cofactor. The BCAA pathway can be found in many organisms except in mammals. Because of this particularity, microbial production of branched-chain amino acids for animal feed or human supplements is getting more and more attention for economic values. Besides, the BACC pathway can also be engineered to produce isobutanol, which is a potential source of renewable chemicals and fuels.

It can be concluded that ketol-acid reductoisomerase (NADP⁺) is a vital enzyme in the chemical industry. However, the activity assays of ketol-acid reductoisomerase (NADP⁺) using spectrophotometry have not been well established in an industrial scale, although the spectrophotometric assay is considered to be the most reliable and cost-effective method for activity quantification. Fortunately, Creative Enzymes was able to develop the activity assay of utmost quality. We are committed to being the most reliable service provider for enzyme activity assays in the global market. Our prompt service, good customer care, and dedicated approaches have made us a most preferred vendor to our competitors.

Figure: The crystal structure of ketol-acid reductoisomerase from Slackia exigua in complex with NADP⁺.
PDB: 4KQW