The metabolism of glucose in corn coleoptiles in relation to oxygen and 2,4-dinitrophenol

Abstract

[U-14C]glucose was fed in tracer amount to corn coleoptiles and the distribution of 14C was observed after 8.5 h in air, 5% oxygen (extinction point), or nitrogen, in the presence or absence of 2,4-dinitrophenol 9 × 10−6 M. Restriction of oxygen caused increased loss of labelled sugars, mainly between the extinction point and zero oxygen. This accounted for about half of the increase in 14CO2 and [14C]ethanol, the rest resulting from diversion of 14C from synthesis of insoluble tissue compounds. Addition of 2,4-dinitrophenol produced similar results. The data are consistent with current theories of the relation of oxygen and oxidative phosphorylation to the regulation of glycolytic reactions but indicate additional effects in the tissue.The metabolism of exogenous [14C]glucose did not represent that of endogenous substrate. At the extinction point, CO2 from respiration of unlabelled endogenous substrate was less than in air while, 14CO2 from exogenous substrate was greater. The existence and the possible nature of an overriding control of glycolysis in the aerobic state of the tissue are considered.