Krebs Cycle Activity of Mitochondria from Endosperm of Sugar Pine Seed (Pinus Lambertiana Dougl.).

Abstract

Mitochondria from the haploid endosperm (female gametophyte) of sugar pine contain the enzymes of the Krebs cycle. Of the cofactors tested, only adenosine monophosphate (AMP) was required for maximum oxidation of succinate, while Mg++, AMP, and diphosphopyridine nucleotide (DPN+) were required for the oxidation of citrate. Pyruvate-2-C14 and acetate-2-C-14 were metabolized by mitochondria. The absorption of water by the endosperm tissue was accompanied by the activation of the Krebs cycle enzyme system. The capacity of mitochondrial particles to oxidize succinate decreased as the embryos germinated; their ability to oxidize citrate and [alpha]-ketor glutarate increased. The possible physiological significance of changes in particulate enzyme activity, as related to water uptake by the germinating seed, is discussed.