Isolation and characterization of pyruvate decarboxylase from germinating bean seeds (Vicia faba)
Leblova, S.; Martinec, J.
Biologia (Bratislava) 42(12): 1181-1189
ISSN/ISBN: 0006-3088 Accession: 001624428
Pyruvate decarboxylase (PDC) was isolated from V. faba seeds germinated for 3 days by using a procedure that included extraction of the homogenate by a sodium phosphate buffer containing mercaptoethanol, subsequent fractionation of the extract by (NH4)2SO4, desalting by dialysis and DEAE-cellulose chromatography. The enzyme preparation had a specific activity of 161 U/mg protein. Both purity of the enzyme preparation of PDC and temp. affected preparation stability. The isolated PDC had pH and temp. optima of 5.7 and 58 degrees C, resp. At this pH, the enzyme exhibited Michaelis-Menten kinetics with Km equal to 4.9 mM whereas at other pH values the function was sigmoidal with S0.5 of 7.9-16.2 mM. Hill coeff. values were between 1.4 (at the pH optimum) and 2.1 (at pH 7.0). 10 mM Cd2+ significantly inhibited PDC, while Cu2+, Co2+ and Ni2+ at the same concn did not affect enzyme activity and may substitute for Mg2+ as PDC cofactor. The regulatory role of PDC in the metabolism of germinating seeds as well as the effects of heavy metals are discussed.