Enzyme Activity of Mitochondria from Germinating Seedlings of Sugar Pine (Pinus Lambertiana Dougl.).

Abstract

Particulate cellular fractions were separated from seedlings and embryos of sugar pine (Pinus lambertiana). The particles centrifuging between 2,000 and 20,000 x g catalyzed the oxidation of acids of the Krebs cycle. The cofactor requirements, and effects of malonate on these oxidations, indicated that the particles are similar to mitochondria isolated from other plants and animals. This is the first such report for Gymnosperm species. Pyruvate-2-C14 and acetate-2-C14 were metabolized by mitochondria from sugar pine. Malic, citric, and succinic acids isolated from the reaction mixture were radioactive. Alanine-1-C14 and alanine-3-C14 were metabolized by the mitochondria of sugar pine, and radioactive CO2 was produced. Pyruvic, citric and succinic acids isolated from the reaction mixture were radioactive. The metabolism of palmitate-1-C14 and butyrate-1-C14 by pine mitochondria and microsomes indicated the presence of mechanisms for the oxidation of fatty acids. The mitochondria from the embryos of ungerminated pine seeds showed a higher oxidative activity on various Krebs cycle substrates than particles from 5-day-old germinated seedlings, or particles from embryos of seeds stratified 60 or 120 days. The mitochondria which showed decreasing oxidative activity with seedling development were stimulated by the supernatant from ungerminated seeds from which the mitochondria were removed. The stimulating factor was not present in the microsomes or the ash; it was stable to heat, unstable to acid and alkali, and not replaceable by flavin nucleotides.