THE METABOLISM OF l-LYSINE-6-C14

The metabolism of ring-labeled L-thyroxine-C14 in vivo.

In the past, investigators have used thyroxine labeled either with JIP" in the 3',5'-position or with C14 in the carboxyl position to study the metabolism of thyroxine in vivo. Although these studies have yielded much valuable information, our knowledge about the metabolic fate of the ring structure in thyroxine is incomplete because both the 3'5'-IJ13 and the carboxyl-C14 are rapidly removed f...

Metabolism of L-ascorbic acid-1-C14 in man.

n-Ascorbic acid labeled with Cl4 has been utilized in studying the metabolism of this vitamin in rats (1, 2) and guinea pigs (3, 4). In both species there is considerable conversion of carboxyl-labeled n-ascorbic acid to CO2 and significant urinary excretion of labeled oxalate. The important nutritional role of n-ascorbic acid made it desirable to study the metabolism of the labeled vitamin in ...

Plasma Protein Labeled with Lysine-ε-c14

The metabolism of homologous plasma proteins, labeled with lysine-epsilon-C(14), after oral administration to dogs has been investigated. The speed of the various processes involved is indicated by the maximum rate of C(14) O(2) excretion which is attained within 1 to 4 hours, the prompt appearance of protein activity in the plasma and disappearance of non-protein activity from it, both virtual...

Metabolism of Coprostanol-c14 and Cholestanol-4-c14 in Man.

Biotransformation of L-lysine to L-pipecolic acid catalyzed by L-lysine 6-aminotransferase and pyrroline-5-carboxylate reductase.

The enzyme involved in the reduction of delta1-piperideine-6-carboxylate (P6C) to L-pipecolic acid (L-PA) has never been identified. We found that Escherichia coli JM109 transformed with the lat gene encoding L-lysine 6-aminotransferase (LAT) converted L-lysine (L-Lys) to L-PA. This suggested that there is a gene encoding "P6C reductase" that catalyzes the reduction of P6C to L-PA in the genome...