Abstract
The ability of chicken retina and retinal pigment epithelium (RPE) membrane to hydrolyze vitamin A esters ([9,10-3H]all-trans- and 11-cis- retinyl palmitate) was studied. Hydrolytic activity within the retina was optimal at acidic pH of 5.0, whereas in the RPE significant hydrolytic activity was exhibited over a broad range of hydrogen ion concentrations. The highest rate of hydrolysis was associated with the all-trans-isomer and located within retina and RPE membranes [the apparent maximal velocity (V(max)) and Michaelis-Menten constant (K(m)) were 770 pmol · min · -1 · mg-1 and 45 μM and 300 pmol · min · -1 · mg-1 and 3.6 μM, respectively]. Retinyl ester hydrolase activities for 11-cis-retinyl palmitate in the retina and RPE were correspondingly lower (apparent V(max) of 204 pmol · min · -1 · mg-1 and K(m) of 18.5 μM in the retina; apparent V(max) of 131 pmol · min · -1 · mg-1 and K(m) of 4 μM in the RPE). Together with results from other laboratories, results from the present study suggest that chicken retina contains important enzymes to complete the visual cycle.
Original language | English (US) |
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Pages (from-to) | R1346-R1350 |
Journal | American Journal of Physiology - Regulatory Integrative and Comparative Physiology |
Volume | 269 |
Issue number | 6 38-6 |
DOIs | |
State | Published - 1995 |
Keywords
- enzymes
- retina
- retinyl pigment epithelium
- vitamin A
ASJC Scopus subject areas
- Physiology
- Physiology (medical)