GLycolytic enzymes were studied from normal human retinas (both fetal and adult) and from retinoblastomas of eight patients and an established retinoblastoma cell line. No significant differences were found between the enzyme activities in the tissues investigated except for hexokinase and pyruvate kinase, which were significantly decreased in the tumor cells. In fetal retina, five different fo...

Inhibition of mammalian hexokinase by glucose g-phosphate was first reported by Weil-Malherbe and Bone (1) and studied by Crane and Sols (2). An inhibition of rabbit muscle phosphofructokinase by excess adenosine triphosphate was observed by Lardy and Parks (3) and was shown to be reversed by a number of intracellular components by Passonneau and Lowry (4). Similar findings were reported on the...

Glucokinase regulates insulin secretion by controlling the rate of glucose phosphorylation. In this report we utilize islets transgenic for high affinity yeast hexokinase to examine the role of glucose phosphorylation on other beta cell functions. Normal pancreatic islets responded to culture in low glucose by lowering insulin synthetic rates, becoming depleted of insulin and insulin mRNA, losi...

The mechanism of calf brain hexokinase has recently been studied in our laboratory (1). It was concluded from kinetic experiments that adenosine diphosphate (ADP) dissociates from the enzyme before addition of substrate glucose. This hypothesis was supported by kinetic studies of n-mannose, ADP, and glucose g-phosphate inhibition. The experiments appear to lend credence to theories in which an ...

Lenses from 100 gram albino rats remain clear and possess normal levels of Na+, K+, ATP, and hexokinase activity for 20 hours incubated in medium containing 12 mM glucose. Below 2.0 mM glucose, a cataract forms and there is an abrupt rise in lens Na+ and wet weight, a fall in lens K+, ATP, and hexokinase activity. The cataract is a thin lamellar opacity involving the anterior and posterior surf...

In a series of previous papers (l-5) studies on the crystalline yeast hexokinase prepared by the method of Darrow and Colowick (6) have been reported. It has been shown (2) that the yeast hexokinase has a weak but distinct adenosine triphosphatase activity and that the ratio of these two activities of the enzyme stayed constant through six recrystallizations. It was furthermore shown (5) that t...

Voltage-dependent anion-selective channel proteins (VDACs) are pore-forming proteins found in the outer mitochondrial membrane of all eukaryotes and in brain postsynaptic membranes. VDACs regulate anion fluxes of a series of metabolites including ATP, thus regulating mitochondrial metabolic functions. Hexokinase binds to porin. The mitochondrially bound hexokinase can greatly increase the rate ...