Oxidase-peroxidase enzymes of Datura innoxia. Oxidation of reduced nicotinamide-adenine dinucleotide in the presence of formylphenylacetic acid ethyl ester

The oxidase-peroxidase from Datura innoxia which catalyses the oxidation of formylphenylacetic acid ethyl ester to benzoylformic acid ethyl ester and formic acid was also found to catalyse the oxidation of NADH in the presence of Mn2+ and formylphenylacetic acid ethyl ester. NADH was not oxidized in the absence of formylphenylacetic acid ethyl ester, although formylphenylacetonitrile or phenylacetaldehyde could replace it in the reaction. The reaction appeared to be complex and for every mol of NADH oxidized 3-4 g-atoms of oxygen were utilized, with a concomitant formation of approx. 0.8 mol of H2O2, the latter being identified by the starch-iodide test and decomposition by catalase. Benzoylformic acid ethyl ester was also formed in the reaction, but in a nonlinear fashion, indicating a lag phase. In the absence of Mn2+, NADH oxidation was not only very low, but itself inhibited the formation of benzoylformic acid ethyl ester from formylphenylacetic acid ethyl ester. A reaction mechanism for the oxidation of NADH in the presence of formylphenylacetic acid ethyl ester is proposed.

Studies on the product binding sites of the Azotobacter vinelandii ribonucleic acid polymerase

During chain elongation RNA polymerase exists as a ternary DNA-enzyme-RNA complex in which a discrete length of the nascent RNA chain proximal to the 3'-OH terminus will be bound to the product binding site (Krakow, J. S., and Fronk, E. (1969) J. Biol. Chem. 244, 5988). We have utilized the poly[d(A-T)]-directed reaction to determine the length of the nascent poly[r(A-U)] protected from attack by pancreatic ribonuclease. Following release of the ribonuclease resistant oligo[r(A-U)] from the ternary complex, its size was determined by ion exchange chromatography on DEAE-cellulose, gel filtration on Bio-Gel P-10, and the ratio of 3'-terminal uridine to internal 2':3'-UMP following alkaline hydrolysis. The results indicate that the length of the nascent protected fragment is approximately 12 residues.