Hexokinase of calf trabecular meshwork.

Area of Science:

• Biochemistry
• Ocular Physiology
• Enzymology

Background:

• Trabecular meshwork (TM) cellular dysfunction is implicated in glaucoma pathogenesis.
• Understanding TM biochemistry, particularly glycolysis, is crucial for defining normal and abnormal function.
• Hexokinase is a key regulatory enzyme in glycolysis.

Purpose of the Study:

• To characterize hexokinase activity and isoenzymes in calf trabecular meshwork.
• To establish a biochemical baseline for TM cellular function relevant to glaucoma.

Main Methods:

• Hexokinase activity was measured in calf TM homogenates.
• Enzyme activity was enhanced by Triton X-100 treatment.
• Isoenzyme analysis was performed using cellulose acetate and starch gel electrophoresis.
• Kinetic properties (Km values) were determined at saturating ATP concentrations.

Main Results:

• Hexokinase activity was detected in calf TM homogenates.
• Triton X-100 treatment increased measurable hexokinase activity twofold.
• Cellulose acetate electrophoresis revealed hexokinase types I and II.
• Starch gel electrophoresis further resolved type 1 into adult and fetal subtypes, with type 1 being predominant.
• Calculated Km values for hexokinase were 7.15 X 10(-2) M, 1.78 X 10(-3) M, and 1.19 X 10(-4) M.
• Most TM hexokinase isoenzymes resemble those in other ocular and extraocular tissues.

Conclusions:

• Calf trabecular meshwork possesses hexokinase activity with distinct isoenzyme profiles.
• The presence of fetal and adult forms of type I hexokinase suggests potential regulatory roles in TM glycolysis.
• Further research is needed to elucidate the specific function of the fetal isoenzyme in TM biochemistry and its relation to glaucoma.