A Soluble Pyridine Nucleotide Oxidase System from Barley Roots.

Open Access
Publisher Website
Google Scholar
Abstract
The supernatant fraction obtained by high-speed centrifugation (144,000 x G for 20 minutes) of barley root homogenates catalyzes the rapid enzymatic oxidation of reduced pyridine nucleotides. Crude preparations of the oxidase require no added co-factors to catalyze the oxidation of reduced diphosphopyridine nucleotide (DPNH) with the uptake of 0.5 mole 02/mole, but the rate is greatly increased by addition of a boiling water extract of barley roots. Such extracts are also effective in reactivating oxidase preparations after inactivation by dialysis. These effects could not be duplicated by extracts of barley root ash or of barley seed, or by any of several co-factor preparations. Hordenine and tyramine, phenolic amines found in barley roots, accelerate both the rate of DPNH disappearance and O2 uptake, but cause no stoichiometric changes. These compounds may be naturally occurring cofactors of the oxidase system, but a requirement for additional cofactors is indicated. The oxidase system is inhibited by cyanide, ascorbic acid, diethyldithiocarbamate, and by various ortho-dihydric phenols; it is accelerated by hordenine, tyramine, and some other monohydric phenols. Non-phenolic derivatives of the inhibitory or acceleratory phenols are relatively innocuous. The terminal oxidase of the system has not been identified.

This publication has 22 references indexed in Scilit: