Publications

• Cyp27c1 Red-Shifts the Spectral Sensitivity of Photoreceptors by Converting Vitamin A1 into A2.

  Enright J.M., Toomey M.B., Sato S.Y., Temple S.E., Allen J.R., Fujiwara R., Kramlinger V.M., Nagy L.D., Johnson K.M., Xiao Y., How M.J., Johnson S.L., Roberts N.W., Kefalov V.J., Guengerich F.P., Corbo J.C.

  Some vertebrate species have evolved means of extending their visual sensitivity beyond the range of human vision. One mechanism of enhancing sensitivity to long-wavelength light is to replace the 11-cis retinal chromophore in photopigments with 11-cis 3,4-didehydroretinal. Despite over a century ... >> More

  Some vertebrate species have evolved means of extending their visual sensitivity beyond the range of human vision. One mechanism of enhancing sensitivity to long-wavelength light is to replace the 11-cis retinal chromophore in photopigments with 11-cis 3,4-didehydroretinal. Despite over a century of research on this topic, the enzymatic basis of this perceptual switch remains unknown. Here, we show that a cytochrome P450 family member, Cyp27c1, mediates this switch by converting vitamin A1 (the precursor of 11-cis retinal) into vitamin A2 (the precursor of 11-cis 3,4-didehydroretinal). Knockout of cyp27c1 in zebrafish abrogates production of vitamin A2, eliminating the animal's ability to red-shift its photoreceptor spectral sensitivity and reducing its ability to see and respond to near-infrared light. Thus, the expression of a single enzyme mediates dynamic spectral tuning of the entire visual system by controlling the balance of vitamin A1 and A2 in the eye. << Less

  Curr. Biol. 25:3048-3057(2015) [PubMed] [EuropePMC]

• Human cytochrome P450 27C1 catalyzes 3,4-desaturation of retinoids.

  Kramlinger V.M., Nagy L.D., Fujiwara R., Johnson K.M., Phan T.T., Xiao Y., Enright J.M., Toomey M.B., Corbo J.C., Guengerich F.P.

  In humans, a considerable fraction of the retinoid pool in skin is derived from vitamin A2 (all-trans 3,4-dehydroretinal). Vitamin A2 may be locally generated by keratinocytes, which can convert vitamin A1 (all-trans retinol) into vitamin A2 in cell culture. We report that human cytochrome P450 (h ... >> More

  In humans, a considerable fraction of the retinoid pool in skin is derived from vitamin A2 (all-trans 3,4-dehydroretinal). Vitamin A2 may be locally generated by keratinocytes, which can convert vitamin A1 (all-trans retinol) into vitamin A2 in cell culture. We report that human cytochrome P450 (hP450) 27C1, a previously 'orphan' enzyme, can catalyze this reaction. Purified recombinant hP450 27C1 bound and desaturated all-trans retinol, retinal, and retinoic acid, as well as 11-cis-retinal. Although the physiological role of 3,4-dehydroretinoids in humans is unclear, we have identified hP450 27C1 as an enzyme capable of efficiently mediating their formation. << Less

  FEBS Lett. 590:1304-1312(2016) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.

• Human mitochondrial cytochrome P450 27C1 is localized in skin and preferentially desaturates trans-retinol to 3,4-dehydroretinol.

  Johnson K.M., Phan T.T.N., Albertolle M.E., Guengerich F.P.

  Recently, zebrafish and human cytochrome P450 (P450) 27C1 enzymes have been shown to be retinoid 3,4-desaturases. The enzyme is unusual among mammalian P450s in that the predominant oxidation is a desaturation and in that hydroxylation represents only a minor pathway. We show by proteomic analysis ... >> More

  Recently, zebrafish and human cytochrome P450 (P450) 27C1 enzymes have been shown to be retinoid 3,4-desaturases. The enzyme is unusual among mammalian P450s in that the predominant oxidation is a desaturation and in that hydroxylation represents only a minor pathway. We show by proteomic analysis that P450 27C1 is localized to human skin, with two proteins of different sizes present, one being a cleavage product of the full-length form. P450 27C1 oxidized all-<i>trans</i>-retinol to 3,4-dehydroretinol, 4-hydroxy (OH) retinol, and 3-OH retinol in a 100:3:2 ratio. Neither 3-OH nor 4-OH retinol was an intermediate in desaturation. No kinetic burst was observed in the steady state; neither the rate of substrate binding nor product release was rate-limiting. Ferric P450 27C1 reduction by adrenodoxin was 3-fold faster in the presence of the substrate and was ∼5-fold faster than the overall turnover. Kinetic isotope effects of 1.5-2.3 (on <i>k</i>_cat/<i>K_m</i> ) were observed with 3,3-, 4,4-, and 3,3,4,4-deuterated retinol. Deuteration at C-4 produced a 4-fold increase in 3-hydroxylation due to metabolic switching, with no observable effect on 4-hydroxylation. Deuteration at C-3 produced a strong kinetic isotope effect for 3-hydroxylation but not 4-hydroxylation. Analysis of the products of deuterated retinol showed a lack of scrambling of a putative allylic radical at C-3 and C-4. We conclude that the most likely catalytic mechanism begins with abstraction of a hydrogen atom from C-4 (or possibly C-3) initiating the desaturation pathway, followed by a sequential abstraction of a hydrogen atom or proton-coupled electron transfer. Adrenodoxin reduction and hydrogen abstraction both contribute to rate limitation. << Less

  J. Biol. Chem. 292:13672-13687(2017) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.