Kinetic models for synthesis by a thermophilic alcohol dehydrogenase

Journal Article · Thu Jul 01 00:00:00 EDT 1993 · Biotechnology and Bioengineering; (United States)

DOI:https://doi.org/10.1002/bit.260420314· OSTI ID:6364812

Ford, J B; Askins, K J; Taylor, K B ^[1]

---

1. Univ. of Alabama, Birmingham (United States)

Alcohol dehydrogenase from Thermoanearobium brockii at 25[degree] C and at 65[degree]C is more active with secondary than primary alcohols. The enzyme utilizes NADP and NADPH as cosubstrates better than NAD and NADH. The maximum velocities (V[sub m]) for secondary alcohols at 65[degree] C are 10 to 100 times higher than those at 25[degree] C, whereas the K[sub m] values are more comparable. At both 25[degree] C and 65[degree] C the substrate analogue 1,1,1,3,3,3-hexafluoro-2-propanol inhibited the oxidation of alcohol competitively with respect to cyclopentanol, and uncompetitively with respect to NADP. Dimethylsulfoxide inhibited the reduction of cyclopentanone competitively with respect to cyclopentanone, and uncompetitively with respect to NADPH. As a product inhibitor, NADP was competitive with respect to NADPH. These results demonstrate that the enzyme binds the nucleotide and then the alcohol or ketone to form a ternary complex which is converted to a product ternary complex that releases product and nucleotide in that order. At 25[degree] C, all aldehydes and ketones examined inhibited the enzyme at concentrations above their Michaelis constants. The substrate inhibition by cyclopentanone was incomplete, and it was uncompetitive with respect to NADPH. Furthermore, cyclopentanone as a product inhibitor showed intercept-linear, slope-parabolic inhibition with respect to cyclopentanol. These results indicate that cyclopentanone binds to the enzyme-NADP complex at high concentrations. The resulting ternary complex slowly dissociates NADP and cyclopentanone. At 65[degree] C, all of the secondary alcohols, with the exception of cyclohexanol, show substrate activation at high concentration.

• OSTI ID: 6364812
• Journal Information: Biotechnology and Bioengineering; (United States), Vol. 42:3; ISSN 0006-3592
• Country of Publication: United States
• Language: English

Related Subjects

09 BIOMASS FUELS
ALCOHOL DEHYDROGENASE
BIOSYNTHESIS
ALCOHOLS
YIELDS
BACTERIA
GROWTH
BIOCHEMICAL REACTION KINETICS
ENZYMATIC HYDROLYSIS
ENZYME INHIBITORS
NADP
NUCLEOTIDES
CHEMICAL REACTIONS
COENZYMES
DECOMPOSITION
ENZYMES
HEMIACETAL DEHYDROGENASES
HYDROLYSIS
HYDROXY COMPOUNDS
KINETICS
LYSIS
MICROORGANISMS
ORGANIC COMPOUNDS
OXIDOREDUCTASES
PROTEINS
REACTION KINETICS
SOLVOLYSIS
SYNTHESIS
090900* - Biomass Fuels- Processing- (1990-)