Hexokinase activating factor

A rather curious activating factor which increases the activity of brain, muscle, and yeast hexokinases to different extents has been isolated from erythrocytes of man. The activator is nondialyzable, strongly associated with proteinaceous material, and loses activity on exposure to 80 to 100 C. It does not appear to be a glycolytic enzyme nor does it increase synthesis of ATP, stabilize ATP, or remove inhibitory products. 

Several different changes in mitochondria occur during apoptosis. These include a change in membrane potential (usually depolarization), increased production of reactive oxygen species, potassium channel activation, calcium ion uptake, increased membrane permeability and release of cytochrome c and apoptosis inducing factor (AIF) [25]. Increased permeability of the mitochondrial membranes is a pivotal event in apoptosis and appears to result from the formation of pores in the membrane the proteins that form such permeability transition pores (PTP) may include a voltage-dependent anion channel (VDAC), the adenine nucleotide translocator, cyclophilin D, the peripheral benzodiazepine receptor, hexokinase and... 

Yet another way to alter the effective activity of an enzyme is to change the accessibility of its substrate. The hexokinase of muscle cannot act on glucose until the sugar enters the myocyte from the blood, and the rate at which it enters depends on the activity of glucose transporters in the plasma membrane. Within cells, membrane-bounded compartments segregate certain enzymes and enzyme systems, and the transport of substrate into these compartments may be the limiting factor in enzyme action. 

Metal-activated en mes Some enzymes collaborate with soluble metal ion co-factors, for example Mg, Mg combines with ATP to provide the substrate for kinase reactions, e.g. hexokinase. 

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