Microsomal retinal synthesis: retinol vs. holo-CRBP as substrate and evaluation of NADP, NAD and NADPH as cofactors

doi:10.1016/0167-4838(92)90267-H

Biochimica et Biophysica Acta (BBA) - Protein Structure and Molecular Enzymology

Volume 1120, Issue 2, 8 April 1992, Pages 183-186

https://doi.org/10.1016/0167-4838(92)90267-H Get rights and content

Holo-CRBP (cellular retinol binding protein) is recognized specifically by an NADP-dependent microsomal retinol dehydrogenase and protects retinol from conversion into retinal by NAD and NADPH dependent dehydrogenases. The synthesis of retinal from free retinol is catalyzed by both NADP- and NAD-dependent pathways, with the former being the preferred one (K_m of 4 vs. 22 μM for retinol, and V_max/K_m of 33 vs. 9, respectively). NADPH does not support quantitatively significant retinal synthesis from physiological concentrations of retinol or holo-CRBP, if an NADPH regenerating system is used to prevent NADP formation.

References (18)

NapoliJ.L.
J. Biol. Chem.
(1986)
NicotraC. et al.
J. Biol. Chem.
(1982)
NapoliJ.L. et al.
Arch. Biochem. Biophys.
(1987)
LeoM.A. et al.
Arch. Biochem. Biophys.
(1987)
PoschK.C. et al.
Arch. Biochem. Biophys.
(1989)
NapoliJ.L. et al.
Biochim. Biophys. Acta
(1990)
OngD.E. et al.
J. Biol. Chem.
(1988)
YostR.W. et al.
J. Biol. Chem.
(1988)
LevinM.S. et al.
Methods Enzymol.
(1990)

There are more references available in the full text version of this article.

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Retinoic acid is synthesized from retinaldehyde by aldehyde dehydrogenases (ALDHs). These enzymes catalyze the oxidation of various endogenous and exogenous substrates and differ in subcellular localization, substrate preference, charge, and inhibitor susceptibility (Napoli and Race 1987; Posch et al. 1989; Napoli et al. 1992). Retinaldehyde is thought to be an important substrate of a class 1 (cytosolic) ALDH named ALDH1 in rats, AHD2 in mice, and E1 in humans (Greenfield and Pietruszko 1977).
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Microsomal retinal synthesis: retinol vs. holo-CRBP as substrate and evaluation of NADP, NAD and NADPH as cofactors

J. Biol. Chem.

J. Biol. Chem.

Arch. Biochem. Biophys.

Arch. Biochem. Biophys.

Arch. Biochem. Biophys.

Biochim. Biophys. Acta

J. Biol. Chem.

J. Biol. Chem.

Methods Enzymol.