Investigation of lens glycolytic enzymes: Species distribution and interaction with supramolecular order

Distribution of several glycolytic enzymes in the lenses of different vertebrate species and theirorganization in the calf lenses were studied. Though no general pattern of enzyme activities in different species is discernible, high activities of TPI followed, in decreasing order, by GAPDH, enolase, PK, LDH and aldolase appear to be more common. Our observation on the unusually high activities of aldolase in the pig, enolase in the sheep and LDH in the duck lens are interesting in view of the already known dual function of LDH as an enzyme and a structural protein ( ε-crystallin) in duck. Controlled treatment with detergents Brij-58 and Triton X-100 caused distinctly differential purturbations in the lens cells. In spite of fiber membrane disruption and partial actin dissolution by Brij-58, no significant increase in the release of glycolytic enzymes compared to control was observed. This suggests that none of the enzymes existed as a completely soluble and freely diffusible fraction. But treatment with a strong detergent (Triton X-100) caused the release of higher amounts of enzymes suggesting either a direct or indirect interaction with the cytomatrix components. Aldolase appears to be maximally bound in the cytosol followed by TPI, GAPDH, LDH and PK in decreasing order. Although thin lens slices were incubated with the detergents for a total period of 40 min and the loss of fiber architecture and organization confirmed by light microscopy, in the Triton- X-100 treated tissues less than 25% of the total activity of any enzyme except TPI appeared in the bathing medium. Such a restricted diffusion of enzymes from the tissues suggests significant protein-protein interactions. The present study indicates highly variable activities of glycolytic enzymes in different species and an ordered array of these enzymes in the cytomatrix.