Identification of the Key Residues Determining the Product Specificity of Isomerohydrolase
Open accessAbstract
The efficient recycling of the chromophore of visual pigments, 11-cis-retinal, through the retinoid visual cycle is an essential process for maintaining normal vision. RPE65 is the isomerohydrolase in retinal pigment epithelium and generates predominantly 11-cis-retinol (11cROL) and a minor amount of 13-cis-retinol (13cROL), from all-trans-retinyl ester (atRE). We recently identified and characterized novel homologues of RPE65, RPE65c, and 13-cis-isomerohydrolase (13cIMH), which are expressed in the zebrafish inner retina and brain, respectively. Although these two homologues have 97% identical amino acid sequences, they exhibit distinct product specificities. Under the same assay conditions, RPE65c generated predominantly 11cROL, similar to RPE65, while 13cIMH generated exclusively 13cROL from atRE substrate. To study the impacts of the key residues determining the isomerization product specificity of RPE65, we replaced candidate residues by site-directed mutagenesis in RPE65c and 13cIMH. Point mutations at residues Tyr58, Phe103, and Leu133 in RPE65c resulted in significantly altered isomerization product specificities. In particular, our results showed that residue 58 is a primary determinant of isomerization specificity, because the Y58N mutation in RPE65c and its reciprocal N58Y mutation in 13cIMH completely reversed the respective enzyme isomerization product specificities. These findings will contribute to the elucidation of molecular mechanisms underlying the isomerization reaction catalyzed by RPE65.
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The pathogenesis of RPE65 retinopathy combines local vitamin A deficiency and impaired metabolism, leading to formation of toxic byproducts.
“The pathogenesis, therefore, combines local vitamin A deficiency and its impaired metabolism, which leads to the formation of toxic byproducts.”
From The Role of Vitamin A in Retinal Diseases (2022) · cites this paper as [110]
The Discussion (page not provided) says that RPE65 mutations disrupt the visual cycle and that depletion of the retinal chromophore 11-cis retinal contributes to vision loss and photoreceptor death. This supports impaired metabolism and a local deficiency, but the paper does not say that these changes form toxic byproducts. (LLM, conf=0.88)
Experimental — accuracy not yet measuredPathogenic variants in RPE65 result in 11-cis-retinol and subsequently 11-cis-retinal deficiency, which essentially stops the visual cycle.
“Pathogenic variants in RPE65 result in 11-cis-retinol and subsequently 11-cis-retinal deficiency, which essentially stops the visual cycle.”
From The Role of Vitamin A in Retinal Diseases (2022) · cites this paper as [110]
The Abstract identifies RPE65 as the enzyme that produces 11-cis-retinol, which is then converted to 11-cis-retinal. The Discussion says RPE65 mutations can disrupt the visual cycle and that RPE65 is essential for regenerating 11-cis-retinal. It does not establish that pathogenic variants generally cause both stated deficiencies or essentially stop the cycle; it describes disruption and impaired vision instead. Page numbers are unavailable in our copy. (LLM, conf=0.85)
Experimental — accuracy not yet measuredRPE65 catalyses the conversion of all-trans-retinyl ester to 11-cis-retinol, allowing it to be reused in phototransduction and preventing its conversion to potentially toxic molecules.
“RPE65 catalyses the conversion of all-trans-retinyl ester to 11-cis-retinol, allowing it to be reused in phototransduction and preventing its conversion to potentially toxic molecules.”
From The Role of Vitamin A in Retinal Diseases (2022) · cites this paper as [110]
The Abstract states that RPE65 converts all-trans-retinyl ester to 11-cis-retinol, which is subsequently converted to the chromophore of visual pigments. The Discussion also describes RPE65 as essential to chromophore regeneration. Neither passage supports the added claim that this prevents conversion to potentially toxic molecules. (LLM, conf=0.88)
Experimental — accuracy not yet measuredIn RPE65 retinopathy, retinyl esters accumulate in the RPE, leading to its damage.
“In addition, retinyl esters accumulate in the RPE, leading to its damage [7,108,109,110].”
From The Role of Vitamin A in Retinal Diseases (2022) · cites this paper as [110]
The Abstract says RPE65 converts retinyl esters in the RPE, and the Discussion says RPE65 mutations can disrupt the visual cycle and impair vision. Neither section says retinyl esters accumulate in RPE65 retinopathy or that such accumulation damages the RPE; searches for accumulation and degeneration found no passage addressing that link. (LLM, conf=0.74)
Experimental — accuracy not yet measured
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Mechanism of Lutein to meso -Zeaxanthin Isomerization by RPE65 CatalysisPreprint
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- Authors
- Takahashi, Y., Moiseyev, G., Nikolaeva, O., & Ma, J.-X.
- Affiliations
- University of Oklahoma Health Sciences Center (US)
- Corresponding author
- Ma, Jian-xing
- Venue
- Biochemistry
- Publisher
- American Chemical Society (ACS)
- Published
- 2012-05-14
- Volume
- 51
- Issue
- 20
- Pages
- 4217-4225
- ISSN
- 0006-2960 (ISSN-L)
- 1520-4995
- PMC
- PMC3358571
- OpenAlex
- W165751632
- Cited by
- 13
- References
- 33
- Citations by year
- 2025: 2 · 2024: 4 · 2022: 1 · 2018: 2 · 2016: 2 · 2015: 1 · 2014: 1
- FWCI
- 0.26
- Type
- journal article
- Language
- en
- Open access
- green
- www.ncbi.nlm.nih.gov
- Locations
- Biochemistry (publishedVersion)
- PubMed (publishedVersion)
- Europe PMC (PubMed Central) (acceptedVersion)
- PubMed Central (acceptedVersion)
- Investigative Ophthalmology & Visual Science
- Funders
- National Eye Institute (EY-012231, EY019309, EY-018659, R01EY012231, R01EY018659, R01EY019309)
- National Institute of General Medical Sciences (P20GM104934)
- National Center for Research Resources (P20RR024215)
- Topics
- Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Retinal Development and Disorders
- Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Retinoids in leukemia and cellular processes
- Life Sciences › Neuroscience › Cellular and Molecular Neuroscience › Photoreceptor and optogenetics research
- Keywords
- RPE65, 11-cis-retinol, visual pigments, product specificity, site-directed mutagenesis, zebrafish, retinal pigment epithelium
- MeSH terms
- Retinoid Isomerohydrolase, Amino Acid Sequence, Animals, Chickens, Leucine, Molecular Sequence Data, Phenylalanine, Pigment Epithelium of Eye, Substrate Specificity, Tyrosine, Vitamin A, Zebrafish, Mutagenesis, Site-Directed, cis-trans-Isomerases, Catalytic Domain
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