Characterization of NAD-dependent alcohol dehydrogenase enzymes of strawberry's achenes (Fragaria x ananassa cv. Elsanta) and comparison with respective enzymes from Methylobacterium extorquens

Achenes were isolated from strawberries fruits, while the methylotroph Methylobacterium extorquens (strain with CABI registration number IMI 369321), which has been isolated from strawberry (Fragaria x ananassa cv. Elsanta) callus cultures, was grown on a mixture of methanol (0.25% v/v) and 1,2-propanediol (0.75% v/v). The Alcohol Dehydrogenase (ADH) enzymatic activities of the achenes were assessed and the optimum pH for ADH activity was found to be pH 10.0. Enzyme assays were carried out in order to define the best substrate specificity at pH = 10.0. The best substrates were found to be ethanol (Km = 5.950 mM) and methanol (Km = 12.610 mM). Only enzymes from the bacterium showed capability of using aldehydes – especially formaldehyde – as substrates. A wide variety of metals as well as EDTA and NaN3 were shown to decrease the enzymatic activity. Furthermore, SDS-PAGE Electrophoresis experiments showed Molecular Weight of 47.0 kDa for the Alcohol Dehydrogenase from achenes of strawberries (Fragaria x ananassa). Additional experiments were conducted in order to define certain thermodynamic properties of the enzymes, by using the dehydrogenation activities of these three enzyme sources which were calculated by measuring the absorption of NADH at 340 nm, in the Arrhenius equation.