Rational construction of a 2-hydroxyacid dehydrogenase with new substrate specificity

• Published in: Biochemical and biophysical research communications Vol. 148; no. 1; pp. 15 - 23
• Main Authors: Clarke, Anthony R., Smith, Corinne J., Hart, Keith W., Wilks, Helen M., Chia, William N., Lee, Thomas V., Birktoft, Jens J., Banaszak, Leonard J., Barstow, David A., Atkinson, Tony, Holbrook, J.John
• Format: Journal Article
• Language: English
• Published: San Diego, CA Elsevier Inc 14.10.1987; Elsevier
• Subjects: Alcohol Oxidoreductases - genetics; Alcohol Oxidoreductases - metabolism; Applied sciences; Bacillus stearothermophilus; Binding Sites; Escherichia coli - genetics; Exact sciences and technology; FBP; fructose-1,6-bisphosphate; Geobacillus stearothermophilus - enzymology; Geobacillus stearothermophilus - genetics; Kinetics; L-Lactate Dehydrogenase - genetics; L-Lactate Dehydrogenase - metabolism; lactate dehydrogenase; Lactate Dehydrogenases; LDH; Mutation; Other techniques and industries; Protein Conformation; Substrate Specificity; lactate dehydrogenase; LDH; FBP; fructose-1,6-bisphosphate
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1016/0006-291X(87)91070-9

Using site-directed mutagenesis on the lactate dehydrogenase gene from Bacillus stearothermophilus, three amino acid substitutions have been made at sites in the enzyme which we suggest in part determine specificity toward different hydroxyacids (R-CHOH-COOH). To change the preferred substrates from the pyruvate/lactate pair (R = -CH 3) to the oxaloacetate/malate pair (R = -CH 2-COO −), the volume of the active site was increased (thr 246 → gly), an acid was neutralized (asp-197 → asn) and a base was introduced (gln-102 → arg). The wild type enzyme has a catalytic specificity for pyruvate over oxaloacetate of 1000 whereas the triple mutant has a specificity for oxaloacetate over pyruvate of 500. Despite the severity and extent of these active site alterations, the malate dehydrogenase so produced retains a reasonably fast catalytic rate constant (20 s −1 for oxaloacetate reduction) and is still allosterically controlled by fructose-1,6-bisphosphate.