Glucose phosphorylation in Helicobacter pylori

Abstract

Saccharide kinase activities in Helicobacter pylori were investigated by incubating bacterial lysates with ATP and mono- or disaccharides and monitoring directly the appearance of phosphorylated products using 13C or 31P nuclear magnetic resonance spectroscopy. The monosaccharides employed included two trioses, two tetroaldoses, one tetroketose, five aldopentoses, two ketopentoses, five aldohexoses, three ketohexoses, and gluconic and glucuronic acids; the disaccharides studied were maltose, trehalose, cellobiose, sucrose, lactose, gentobiose, and melibiose. D-Glucose was the only sugar phosphorylated among all the carbohydrates examined. The kinase activity of lysates was studied by measuring the rates of formation of glucose 6-phosphate. The substrate specificity, the relatively high KM, and the absence of substrate inhibition suggested that the enzyme is a glucokinase rather than a hexokinase. Most of the glucose kinase activity was observed with the pellet fraction obtained by centrifugation, suggesting an association of the enzyme with the bacterial cell envelope.