Merrill L. Gassman

Protoheme extraction from plant tissue

A method for reproducibly estimating the protoheme content of plant tissues has been developed. The tissue sample is homogenized in 80% acetone to remove pigments and lipids; protoheme is then extracted from the tissue residue with 2% HCl in acetone and quantitatively transferred into diethyl ether. After evaporation of the ether, the residue is dissolved in alkaline pyridine, and the protoheme concentration is estimated from a dithionite-reduced-minus-ferricyanide-oxidized spectrum. When compared to some other methods, this procedure gives consistently higher yields.

Absorbance and fluorescence properties of protochlorophyllide in etiolated bean leaves

Abstract Primary leaves of 7-to-9 day-old etiolated bean seedlings contain a species of protochlorophyllide which is not transformed to chlorophyllide by light; this pigment species exhibits an absorption peak at 631nm in vivo at −196° and a fluorescence emission peak at 639nm in vivo at room temperature. Heat-treatment of etiolated leaves converts the phototransformable protochlorophyllide holochrome to a pigment species with in vivo absorption and fluorescence peaks identical to those of endogenous nontransformable protochlorophyllide. Administration of δ-amino-levulinic acid to etiolated leaves causes the synthesis of non-transformable protochlorophyllide with an absorption peak also at 631nm in vivo at −196° but with a fluorescence emission peak at 643nm in vivo at room temperature. Heat-treatment of such leaves does not affect the position of these bands. The results indicate that protochlorophyllide which is derived from exogenous δ-amino-levulinic acid is in a physically different state from other forms of protochlorophyllide in the leaf.

Metabolism of [4-14C]levulinic acid by etiolated and greening leaves of Hordeum vulgare

Abstract When etiolated barley (Hordeum vulgare L. var. Larker) shoots are incubated with [4-14C]levulinic acid, 14CO2 is evolved, and amino and organic acids are labelled. Respiratory inhibitors and short-chain fatty acids, similar in size to levulinic acid, reduce the production of 14CO2 from [4-14C]levulinic acid, while δ-aminolevulinic acid treatment or illuminating the tissue increase 14CO2 evolution. The contribution of levulinic acid metabolism to α-aminolevulinic acid biosynthesis is no greater than that of a general cellular metabolite. The data suggest that fatty acid oxidation and the citric acid cycle are involved in levulinic acid metabolism.

Effect of cycloheximide on the catabolism of levulinic acid to CO2 by etiolated leaves of Hordeum vulgare

Abstract When etiolated barley ( Hordeum vulgare L. var. Larker) shoots are incubated with [4- 13 C]levulinic acid, they evolve 14 CO 2 . Cycloheximide inhibits this catabolism, and the effect is distinct from any effect this antimetabolite has on fatty acid oxidation or respiration. We suggest that a protein which is synthesized on 80 S ribosomes and which has a short half-life is necessary for levulinic acid catabolism to CO 2 .