Serine biosynthesis in human hair follicles by the phosphorylated pathway: follicular 3-phosphoglycerate dehydrogenase.
The phosphorylated pathway of serine biosynthesis was demonstrated in human hair bulbs and sheaths by the formation of phosphoserine and serine from (14C)3-phosphoglyceric acid. The initial and rate limiting enzyme of the pathway, 3-phosphoglycerate dehydrogenase (3-PGDH) was demonstrated by enzyme determinations in human and rat hair follicles, human epidermis, and chicken epidermis. Follicular 3-PGDH was characterized using a sensitive fluorometric assay with NADH as a co-substrate. Monovalent cations (Na+, K+, Li+, or NH4+) were necessary for full enzyme activity. p-Hydroxymercuribenzoate inhibited activity, and activity was 3 times higher with NADH as a co-substrate than with NADPH. The apparent Km for the substrate hydroxyphosphopyruvic acid was 32.8 muM, and the apparent Km for NADH 4.8 muM similar to the Kms for other mammalian 3-PGDHs. Enzyme activity was not altered by parenteral corticosteroids, a high carbohydrate diet, low protein diet, or starvation. Enzyme activity decreased over the first 12 days of life in newborn rats. The phosphorylated pathway of serine synthesis provides a potential nondietary and nonhepatic source of serine, glycine, and their products in keratinizing tissues.
D000429:Alcohol Oxidoreductases / Q000378:metabolism*; D000818:Animals; D000831:Animals, Newborn; D002237:Carbohydrate Dehydrogenases / Q000378:metabolism*; D006197:Hair / Q000378:metabolism*; D006801:Humans; D007770:L-Lactate Dehydrogenase / Q000302:isolation & purification; D011506:Proteins / Q000378:metabolism; D011773:Pyruvates / Q000378:metabolism; D012694:Serine / Q000096:biosynthesis*; D012867:Skin / Q000378:metabolism
D011506:Proteins; D011773:Pyruvates; D012694:Serine; D000429:Alcohol Oxidoreductases; D002237:Carbohydrate Dehydrogenases; D007770:L-Lactate Dehydrogenase