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J Preiss

Publications and source records attributed to J Preiss.

At least 235 records · Page 13Linked to original sources
PubMed1969

Presence of ADP-Glucose Pyrophosphorylase in Shrunken-2 and Brittle-2 Mutants of Maize Endosperm.

ADP-Glucose pyrophosphorylase activity has been detected in relatively low amounts in the embryos and endosperms of sh(2) and bt(2) mutant maize seeds. The total enzyme activities in sh(2) and bt(2) were about 12% and 17% respectively, of that found in starchy maize seeds (Dekalb 805). The ADP-glucose pyrophosphorylases from the starchy and mutant maize seeds were activated by 3-phosphoglycerate. However, the extent of the activation of the sh(2) enzyme was not as great as that observed with the bt(2) and Dekalb 805 enzymes. The low levels of ADP-glucose pyrophosphorylase activity in the maize mutants correlate well with the low levels of starch found in the endosperm of these mutants.

Journal Article↗
PubMed1968

Regulation of starch biosynthesis in plant leaves: activation and inhibition of ADPglucose pyrophosphorylase.

The ADPglucose pyrophosphorylases of 7 plant-leaf tissues were partially purified and characterized. In all cases the enzymes showed stability to heat treatment at 65 degrees for 5 minutes in the presence of 0.02 m phosphate buffer, pH 7.0. The leaf ADPglucose pyrophosphorylases were activated 5 to 15-fold by 3-phosphoglycerate. Fructose-6-phosphate and fructose 1, 6-diphosphate stimulated ADPglucose pyrophosphorylase to lesser extents. The A(0.5) (conc of activator required to give 50% of the observed maximal activation) of 3-phosphoglycerate for the barley enzyme was 7 x 10(-6)m while for the sorghum enzyme it was 3.7 x 10(-4)m. Inorganic phosphate proved to be an effective inhibitor of ADPglucose synthesis. The I(0.5) (conc of inhibitor that gave 50% inhibition of activity for the various leaf enzymes varied from 2 x 10(-5)m (barley) to 1.9 x 10(-4)m (sorghum). This inhibition was reversed or antagonized by the activator 3-phosphoglycerate. These results form the basis for an hypothesis of the regulation of leaf starch biosynthesis.

Glucosyltransferases↗