Studies on vitamin A: 5. The preparation of retinene(1)-vitamin A aldehyde.

A comparison of retinene reductase and alcohol dehydrogenase of rat liver.

Retinene reductase, an enzyme which catalyzes the diphosphopyridine nucleotide-dependent reduction of vitamin A aldehyde (retinene) to vitamin A alcohol, was first demonstrated with homogenates of frog and cattle retinas (1, 2). Because crude rabbit liver extracts (3) and crystalline horse liver alcohol dehydrogenase (4) catalyze the oxidation of vitamin A into retinene, the general involvement...

Studies in vitamin A. 6. Conversion in vivo of vitamin A aldehyde (retinene(1)) to vitamin A(1).

Metabolism of the retina. III. The role of reduced triphoshopyridine nucleotide in the visual cycle.

Exposure of a dark-adapted retina to light results in the liberation of vitamin A aldehyde (retinene) from the visual pigment, rhodopsin, and in subsequent enzymatic reduction of the liberated aldehyde to vitamin A (1). The enzyme, alcohol dehydrogenase (retinene reductase), is present in visual cell outer segments and can use reduced diphosphopyridine nucleotide (DPNH) for the reduction of vit...

The Reduction of Retinene1 to Vitamin A1 in Vitro

In the surviving vertebrate retina the retinene(1) liberated by bleaching rhodopsin is converted quantitatively to vitamin A(1). Recent chemical studies have indicated that in this process the aldehyde group of retinene(1) is reduced to the primary alcohol group of vitamin A(1) (Morton; Wald). Some time ago we brought this reaction into a cell-free brei prepared from cattle retinas. The retinas...

Studies in Vitamin A 22 . OPPENAUER OXIDATION OF VITAMIN

The merit of the Oppenauer oxidation (Oppenauer, 1937; reviewed by Djerassi, 1951) using aluminium alkoxides and a hydrogen acceptor, is that unsaturated alcohols can be converted to aldehydes and ketones without affecting the ethylenic linkages. Applied to vitamin A alcohol it ought to yield retinene, (vitamin A1 aldehyde) as the primary product. Hawkins & Hunter (1944a), using aluminium isopr...