scholarly journals Solubilization and Partial Purification of Retinyl Ester Synthetase and Retinoid Isomerase from Bovine Ocular Pigment Epithelium

1989 ◽  
Vol 264 (16) ◽  
pp. 9231-9238 ◽  
Author(s):  
R J Barry ◽  
F J Cañada ◽  
R R Rando
Keyword(s):  
Pigment Epithelium ◽  
Partial Purification ◽  
Retinyl Ester ◽  
Ester Synthetase

scholarly journals Noninvasive two-photon imaging reveals retinyl ester storage structures in the eye

2004 ◽  
Vol 164 (3) ◽  
pp. 373-383 ◽  
Author(s):  
Yoshikazu Imanishi ◽  
Matthew L. Batten ◽  
David W. Piston ◽  
Wolfgang Baehr ◽  
Krzysztof Palczewski
Keyword(s):  
Pigment Epithelium ◽  
Retinal Pigment ◽  
Photoreceptor Cells ◽  
Retinyl Ester ◽  
Two Photon Microscopy ◽  
Two Photon ◽  
In Vivo Experiments ◽  
Essential Components ◽  
Intracellular Compartments

Visual sensation in vertebrates is triggered when light strikes retinal photoreceptor cells causing photoisomerization of the rhodopsin chromophore 11-cis-retinal to all-trans-retinal. The regeneration of preillumination conditions of the photoreceptor cells requires formation of 11-cis-retinal in the adjacent retinal pigment epithelium (RPE). Using the intrinsic fluorescence of all-trans-retinyl esters, noninvasive two-photon microscopy revealed previously uncharacterized structures (6.9 ± 1.1 μm in length and 0.8 ± 0.2 μm in diameter) distinct from other cellular organelles, termed the retinyl ester storage particles (RESTs), or retinosomes. These structures form autonomous all-trans-retinyl ester-rich intracellular compartments distinct from other organelles and colocalize with adipose differentiation-related protein. As demonstrated by in vivo experiments using wild-type mice, the RESTs participate in 11-cis-retinal formation. RESTs accumulate in Rpe65−/− mice incapable of carrying out the enzymatic isomerization, and correspondingly, are absent in the eyes of Lrat−/− mice deficient in retinyl ester synthesis. These results indicate that RESTs located close to the RPE plasma membrane are essential components in 11-cis-retinal production.

On the mechanism of isomerization of ocular retinoids by the crayfish Procambarus clarkii.

1997 ◽  
Vol 200 (3) ◽  
pp. 625-631
Author(s):  
R Srivastava ◽  
T H Goldsmith
Keyword(s):  
Convergent Evolution ◽  
Procambarus Clarkii ◽  
Pigment Epithelium ◽  
Synthetase Activity ◽  
Acyl Transferase ◽  
Phenylmethylsulfonyl Fluoride ◽  
Retinyl Esters ◽  
Vertebrate Eye ◽  
Ester Synthetase ◽  
Hydrolysis Of

The eyes of some crustaceans store substantial amounts of retinyl esters, with most of the retinol in the 11-cis configuration. Earlier work in this laboratory suggested that in lobster and crayfish the mechanism of isomerization of retinol to the 11-cis form involves the hydrolysis of all-trans retinyl esters. Although this is the same process as that occurring in the vertebrate eye, it is different from the retinal photoisomerase reaction known in other arthropods, specifically diurnal insects (Hymenoptera and probably Diptera). Using homogenates of crayfish, we have tested this proposed mechanism by inhibiting retinyl ester synthetase activity in the presence of exogenous all-trans retinol. Inhibition of lecithin:retinol acyl transferase with 5 mumol l-1 retinyl bromoacetate or 2 mmol l-1 phenylmethylsulfonyl fluoride blocks the formation of both all-trans and 11-cis retinyl esters as well as 11-cis retinol, as shown by direct assay and by the decrease in counts derived from tritiated all-trans retinol. The similarity of this isomerization to the mechanism in vertebrate pigment epithelium is thus an interesting example of convergent evolution in the biochemistry of visual pigments, in which the pigments themselves (the opsins) are largely conserved across phyla.

Retinyl esters in the vertebrate neuroretina

1989 ◽  
Vol 256 (1) ◽  
pp. R255-R258 ◽  
Author(s):  
K. A. Rodriguez ◽  
A. T. Tsin
Keyword(s):  
Visual Pigment ◽  
High Performance ◽  
Pigment Epithelium ◽  
Retinal Pigment ◽  
Retinyl Palmitate ◽  
Visual Pigments ◽  
Pigment Synthesis ◽  
Retinyl Ester ◽  
Retinyl Ester Hydrolase ◽  
Retinyl Esters

High-performance liquid chromatography (HPLC) was employed to measure retinyl esters in the vertebrate retina. Both retina and retinal pigment epithelium (RPE) from frog, chicken, and bovine eyes were studied. In comparison to the RPE, the retina possessed a significant level of 11-cis and all trans retinyl palmitate. Using a sensitive radioassay, we also detected the presence of retinyl ester hydrolase (REH) activity in homogenates prepared from both retina and RPE. The rate of retinyl ester hydrolysis in these retinas was sufficiently high to supply retinal chromophores for the metabolic renewal and for the regeneration of visual pigments. In comparison to retinyl esters in the RPE, retinyl esters in the retina are located much closer to the sites of visual pigment synthesis and regeneration. Hence it is possible that these retinyl esters play a more important role in the visual cycle than those in the RPE.

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