Glucose 6-phosphate dehydrogenase of calf trabecular meshwork.

ABSTRACT

Activities of glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase of calf trabecular meshwork were measured and found to be 0.23 and 0.47 mumole/min/g tissue, respectively. Glucose 6-phosphate dehydrogenase was purified 450-fold with a yield of 91% by anion exchange chromatography and 2',5'-ADP agarose affinity chromatography. It was activated by Ca2+, Mg2+, and Mn2+. It was deactivated by p-chloromecuribenzoate, p-chloromercuribenzene sulfonate, and iodoacetamide, but this deactivation could be prevented by pretreatment with cysteine or glutathione. Its rate was regulated by the NADPH/NADP+ ratio, being maximal at a ratio of 0, and negligible at a ratio of 10. At the physiological ratio of 5, its rate was approximately half maximal. On disc gel electrophoresis of both the crude and purified enzyme, seven bands of glucose 6-phosphate dehydrogenase activity could be seen. The isozyme pattern was similar to that of calf retina, but different from that of calf liver. These data suggest that trabecular meshwork is well supplied with the capacity to generate NADPH. Typical demands for NADPH may be to detoxify H2O2 and/or organic peroxides through the glutathione peroxidase/glutathione reductase system, and both generating and removing products of the "killing reaction" during phagocytosis.