γ-Guanidinobutyraldehyde Dehydrogenase of <i>Vicia faba</i> Leaves

gamma-Guanidinobutyraldehyde dehydrogenase was purified 27-fold in 40% yield from extracts of Vicia faba leaves. High specificity exist only for gamma-guanidinobutyraldehyde and gamma-aminobutyraldehyde; the K(m) value was 3.4 micromolar for gamma-guanidinobutyraldehyde, 25 micromolar for gamma-aminobutyraldehyde, and 84 micromolar (case of gamma-guanidinobutyraldehyde) for NAD, respectively. The enzyme had a molecular weight of approximately 83,000. Optimal pH and temperature for activity were 9.5 and 45 degrees C, respectively. The enzyme was inhibited strongly by p-chloromercuribenzoate, N-ethylmaleimide, and zincon (2-carboxy-2'-hydroxy-5'-sulfoformazylbenzene).