STRUCTURE AND KINETIC THERMAL-STABILITY STUDIES OF THE INTERACTION OFMONOHYDRIC ALCOHOLS WITH LIPOXYGENASE-1 FROM SOYBEANS (GLYCINE-MAX)

Monohydric alcohols inhibited the activity of lipoxygenase 1 from soyb ean. The inhibition was reversible and of mixed type. Monohydric alcoh ols increased the Michaelis constant (K-m) and decreased the velocity maximum (V-max). At very low concentrations of alcohols, no structural changes were observed in the enzyme molecule, implicating that the in hibition by monohydric alcohols could be due to the binding of alcohol s at the substrate binding/catalytic site. Monohydric alcohols at high er concentrations induced more ordered structure in the enzyme. The eq uilibrium constants obtained for native to helical intermediate(s) tra nsitions are in the millimolar range and increased with the carbon cha in length of alcohols. The free energy changes for the transitions are small but positive in nature. The environment around aromatic amino a cid residues became more hydrophobic in these alcohols. Alcohols decre ased the thermal stability of lipoxygenase. The activational enthalpy (Delta H-) and activational entropy (Delta S-*) of thermal inactivati on increased in the presence of alcohols.