Solvent effects on the catalytic activity of subtilisin suspended in organic solvents

Journal Article · Sun May 05 04:00:00 EDT 1996 · Biotechnology and Bioengineering

DOI:https://doi.org/10.1002/(SICI)1097-0290(19960505)50:3<257::AID-BIT4>3.0.CO;2-F· OSTI ID:234113

Correa de Sampaio, T; Melo, R B; Moura, T F; Michel, S; Barreiros, S ^[1]

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1. Univ. Nova de Lisboa, Oeiras (Portugal). Inst. de Tecnologia Quimica e Biologica

The authors studied a model transesterification reaction catalyzed by subtilisin Carlsberg suspended in toluene, n-hexane, diisopropyl ether, and mixtures of these solvents. To account for solvent effects due to differences in water partitioning between the enzyme and the bulk solvents, the authors measured water sorption isotherms for the enzyme in each solvent. They measured catalytic activity as a function of enzyme hydration and obtained bell-shaped curves with maxima at the same enzyme hydration in all the solvents. However, the activity maxima were different in all the media, being the lowest in toluene. Differences in the partitioning of substrates and product between the bulk solvent phase and the enzyme active site were accounted for but could not explain the lower catalytic activity observed in toluene. The fact that toluene is very similar to one of the substrates suggested the possibility of competitive inhibition by this solvent. The authors derived a model allowing for differences in solvation of the substrates, by using thermodynamic activities instead of concentrations, as well as for competitive inhibition by toluene. The model fit the experimental data well, confirming that toluene had a direct adverse effect on the catalytic activity of the enzyme.

• OSTI ID: 234113
• Journal Information: Biotechnology and Bioengineering, Journal Name: Biotechnology and Bioengineering Journal Issue: 3 Vol. 50; ISSN BIBIAU; ISSN 0006-3592
• Country of Publication: United States
• Language: English

Related Subjects

56 BIOLOGY AND MEDICINE
APPLIED STUDIES
ADSORPTION ISOTHERMS
BIOLOGICAL EFFECTS
ENZYME ACTIVITY
HEXANE
ISOPROPYL ETHER
PEPTIDE HYDROLASES
TOLUENE