Biomedical subjects

R F McFeeters

Publications and source records attributed to R F McFeeters.

21 records · Page 2Linked to original sources

PubMed1980

Polygalacturonase Activity and Ethylene Synthesis during Cucumber Fruit Development and Maturation.

Polygalacturonase (EC 3.2.1.15) activity in seed cavity tissue from harvested cucumber fruit increased over 20-fold after the fruit had produced a transient burst of ethylene during maturation. This increase was observed in six cucumber cultivars and was present whether polygalacturonase activity was measured at pH 4.6 or 6.2. The seed cavity tissue pH decreased as polygalacturonase activity increased both in ripening fruit and in harvested immature fruit exposed to 10 microliters per liter ethylene in air.

Journal Article↗

PubMed1975

Substrate specificity of chlorophyllase.

Apparent Km and V(max) values were obtained for hydrolysis of methyl and ethyl chlorophyllides a, methyl and ethyl pheophorbide a, and 9-hydroxymethyl pheophorbide a by chlorophyllase from Ailanthus altissima. Analysis of substrate specificity data for chlorophyllase indicates that the presence of a 9-keto group and a methyl alcohol group esterified at the 7-position in chlorophyll derivatives results in maximum binding affinity for substrates. Data on maximum reaction rates indicate that the rate-controlling step of hydrolysis occurs after release of the alcohol from the ester. Probable high affinity chlorophyllase inhibitors can be predicted on the basis of these specificity studies.An improved method for purification of chlorophyllase has been developed.

Journal Article↗

PubMed1971

Purification and Properties of Chlorophyllase from Ailanthus altissima (Tree-of-Heaven).

Chlorophyllase from Ailanthus altissima leaves has been purified 63-fold by a combination of heat treatment, ultracentrifugation, gel filtration, and chromatography on diethylaminoethyl cellulose. While the enzyme is inhibited to some degree by Triton X-100, a modification of the assay procedure of Klein and Vishniac has been shown to be far superior to the use of aqueous acetone systems. The enzyme was found to have a pH optimum on pheophytin a of 4.5. Chlorophylls a and b, pheophytins a and b, and pyropheophytin a were hydrolyzed by the enzyme while protochlorophyll a and 4-vinyl protochlorophyll a were not hydrolyzed but were competitive inhibitors. p-Nitrophenyl acetate was not hydrolyzed. The enzyme does not appear to contain an essential sulfhydryl group since sodium tetrathionate and p-chloromercuribenzoate did not affect its activity.

Journal Article↗