Effect of Cetyltrimethylammonium Bromide on the Activity of Particulate Starch Synthetase from Potato Tuber

Abstract

The action of some detergents on the incorporation of glucose from uridine diphosphate glucose or adenosine diphosphate glucose into the potato tuber starch grain was studied. It was found that the cationic detergent, cetyltrimethylammonium bromide, produces a rapid binding of both sugar nucleotides to the grain and a great increase in the incorporation of glucose into the polysaccharide. Kinetic constants of starch synthetase are also modified, there being an affinity increase for both sugar nucleotides. Neutral detergents are without effect and anionic detergents are inhibitors.In a previous communication (6) on the synthesis of sterylglucosides from UDP-glucose in amyloplasts of sweet corn endosperm, we have found that the cationic detergent, cetyltrimethylammonium bromide, inhibited that synthesis but increased considerably the incorporation of radioactivity into the grains. We have now tried to investigate the latter effect to see if it was related to an increase in the activity of starch synthetase (UDP-glucose: a-1,4-glucan a-4-glucosyltransferase, EC 2.4.1.21) included inside the grain (4,8,12) or to some modification of the permeability of the granule.

Particulate UDP‐glucose: Protein transglucosylase from potato tuber

“…Therefore, the potato particulate fraction would contain the complete system for the formation of the starch granule. According to the data obtained with mature starch grains, the enzymes would be located in a lipid zone [6] and would be able to act in an anhydrous medium [ 131. This fact could explain the formation of such an anhydrous and insoluble structure with two markedly hydrophilic polysaccharides.…”

“…&Amylase Table 1 Table 2 (Sigma) was assayed at pH 5 and a-amylase (saliva source) treatment was carried out in the presence of 0.01 M NaCl. Hydrolysis products were identified by paper chromatography with butanol-pyridine-water (6:4:3) as solvent [5] and paper electrophoresis in pyridine acetate buffer, pH 6.4, for 2 hr at 1000 V. All other materials were as described elsewhere [6].…”

Potato Tuber UDP-Glucose:Protein Transglucosylase Catalyzes Its Own Glucosylation

“…To account for this observation, we proposed that the detergent would confer a positive charge on the latter enzyme. This would produce an increase in the local concentration of negatively charged sugar nucleotide and, hence, an increase in UPTG activity (5,23). On the other hand, Pitcher et al achieved in rabbit muscle preparations the deaggregation of the 86-kD catalytic subunit of glycogen synthase from the 38-kD component in the presence of 2M LiBr (15,16).…”