PMID- 20552438
OWN - NLM
STAT- MEDLINE
DCOM- 20100909
LR  - 20211020
IS  - 1940-6029 (Electronic)
IS  - 1064-3745 (Print)
IS  - 1064-3745 (Linking)
VI  - 652
DP  - 2010
TI  - Analysis of the retinoid isomerase activities in the retinal pigment epithelium 
      and retina.
PG  - 329-39
LID - 10.1007/978-1-60327-325-1_19 [doi]
AB  - Light sensitivity in the vertebrate retina is mediated by the opsin visual 
      pigments inside rod and cone photoreceptor cells. These pigments consist of a G 
      protein-coupled receptor and the photo-sensitive ligand, 11-cis-retinaldehyde 
      (11-cis-RAL). Absorption of a photon by an opsin pigment induces isomerization of 
      the 11-cis-RAL chromophore to all-trans-retinaldehyde (all-trans-RAL), rendering 
      the pigment insensitive to light. The bleached opsin regains light sensitivity by 
      recombining with another 11-cis-RAL. The vertebrate eye contains a biochemical 
      mechanism for regenerating 11-cis-RAL chromophore from all-trans-RAL, called the 
      visual cycle. The visual cycle takes place within cells of the retinal pigment 
      epithelium (RPE). A second visual cycle also appears to be present in Muller 
      glial cells of the retina. A critical step in the regeneration of 11-cis-RAL 
      chromophore is thermal re-isomerization to the 11-cis configuration of an 
      all-trans-retinyl ester (all-trans-RE) or an all-trans-retinol (all-trans-ROL). 
      In RPE cells, this step is carried out by an enzyme called Rpe65 isomerase. This 
      chapter provides methods for assaying Rpe65 isomerase. Although Rpe65 utilizes an 
      all-trans-RE such as all-trans-retinyl palmitate (all-trans-RP) as substrate, it 
      can be assayed in RPE homogenates by providing all-trans-ROL substrate and 
      allowing the endogenous lecithin:retinol acyl transferase (LRAT) to synthesize 
      all-trans-REs using fatty acids from phosphatidylcholine in the membranes. 
      Alternatively, all-trans-RP can be provided directly as substrate, although this 
      requires the isomerase reaction to be carried out in the presence of detergent, 
      since fatty-acyl esters of all-trans-ROL are insoluble. Methods are provided in 
      this chapter for assaying Rpe65 in RPE homogenates with both all-trans-ROL and 
      all-trans-RP substrates. A second visual cycle appears to be present in the 
      retinas of cone-dominant species such as chicken. This retinal pathway may 
      augment the RPE to provide 11-cis-RAL to cone photoreceptors under conditions of 
      bright light where the rate of opsin photoisomerization is high. The isomerase in 
      this pathway (isomerase-2) utilizes all-trans-ROL and palmitoyl coenzyme A (palm 
      CoA) as substrates to synthesize 11-cis-retinyl palmitate (11-cis-RP). 
      Isomerase-2 appears to be present in Muller cells but has not yet been 
      identified. Methods are provided in this chapter for assaying isomerase-2 in 
      chicken retina homogenates.
FAU - Travis, Gabriel H
AU  - Travis GH
AD  - Jules Stein Eye Institute, UCLA School of Medicine, Los Angeles, CA, USA.
FAU - Kaylor, Joanna
AU  - Kaylor J
FAU - Yuan, Quan
AU  - Yuan Q
LA  - eng
GR  - R01 EY011713-15/EY/NEI NIH HHS/United States
GR  - R01 EY011713/EY/NEI NIH HHS/United States
GR  - R01 EY011713-16/EY/NEI NIH HHS/United States
GR  - P30 EY000331/EY/NEI NIH HHS/United States
GR  - R01 EY011713-14/EY/NEI NIH HHS/United States
GR  - P30 EY000331-45/EY/NEI NIH HHS/United States
PT  - Journal Article
PL  - United States
TA  - Methods Mol Biol
JT  - Methods in molecular biology (Clifton, N.J.)
JID - 9214969
RN  - 0 (Diterpenes)
RN  - 0 (Retinyl Esters)
RN  - 11103-57-4 (Vitamin A)
RN  - 1D1K0N0VVC (retinol palmitate)
RN  - EC 3.1.1.64 (retinoid isomerohydrolase)
RN  - EC 5.2.- (cis-trans-Isomerases)
SB  - IM
MH  - Animals
MH  - Cattle
MH  - Chickens
MH  - Chromatography, Liquid
MH  - Diterpenes
MH  - Enzyme Assays/*methods
MH  - Retinal Pigment Epithelium/*enzymology
MH  - Retinyl Esters
MH  - Vitamin A/analogs & derivatives/metabolism
MH  - cis-trans-Isomerases/*metabolism
PMC - PMC3049333
MID - NIHMS268645
EDAT- 2010/06/17 06:00
MHDA- 2010/09/10 06:00
PMCR- 2011/03/07
CRDT- 2010/06/17 06:00
PHST- 2010/06/17 06:00 [entrez]
PHST- 2010/06/17 06:00 [pubmed]
PHST- 2010/09/10 06:00 [medline]
PHST- 2011/03/07 00:00 [pmc-release]
AID - 10.1007/978-1-60327-325-1_19 [doi]
PST - ppublish
SO  - Methods Mol Biol. 2010;652:329-39. doi: 10.1007/978-1-60327-325-1_19.