EVIDENCE FOR GLYCOLYSIS IN BOVINE RETINAL MICROSOMES AND PHOTORECEPTOR OUTER SEGMENTS

Enzymes of the Embden-Meyerhof sequence were found to be associated with bovine retinal outer segment fragments, and also with microsomes probably originating either in the inner segment of the photoreceptor cell or in the pigment epithelium adjacent to the outer segments. Activities of enzymes associated with these membrane fragments were low by comparison with soluble protein derived during membrane isolation. However, enzyme activities of both retinal membrane fragments generally equaled or exceeded those displayed by bovine erythrocytes or liver microsomes. In the case of the photoreceptor outer segment it is inferred that while glycolysis there does not contribute appreciably to the high overall glycolytic activity of the retina, it is probably adequate to provide ATP directly to the sites of ATP hydrolysis in the outer segment membranes. An answer to the question of whether the photoreceptor cell as a unit contributes significantly to retinal glycolysis as some authors have suggested, probably depends upon whether major potions of the very active soluble protein derived from the retina originate in the photoreceptor inner segment. This question is not answered by the present study. © 1969.