METABOLISM OF 3:5 DIIODO-L-THYRONINE BY L-AMINO ACID OXIDASE1

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Abstract
3:5 Diiodo-L-thyronine (20–100 mg.) was incubated with crude L-amino acid oxidase of cobra venom (100–500 mg.) in (A) the absence or (B) the presence of additional catalase (30–120 nig.) for three hours at 37.3° C. (pH 7.4) and incubation mixture extracted with ether at pH 3.0. Chromatography of the ether extract from A in several solvent systems revealed in the main the presence of a phenolic compound, while that from B pointed to the presence of a carbonyl compound and a phenolic compound. The carbonyl compound was identical with an unknown degradation product of an authentic sample of 3:5 diiodothyropyruvic acid as established by chromatography or electrophoresis, color tests and ultraviolet absorbance. The phenolic compound had the same migration on chromatograms or electrophoregrams, and its crystals showed the same ultraviolet absorption and melting point as an authentic sample of 3:5 diiodothyroacetic acid. Under the same experimental conditions, N-chloroacetyl-3:5 diiodo-L-thji-onine, in. which the amino group of 3:5 diiodo-L-thyronine is inactivated with chloroacetjdchloride, is not metabolized to the carbonyl and phenolic compounds. On the basis of these results, it appears that during incubation with L-amino acid oxidase in the presence of large amounts of catalase 3:5 diiodothyroninc is metabolized to 3:5 diiodothyropyruvic acid and that during chromatography and incubation this pyruvic acid derivative is decomposed to an unknown carbonyl compound and to 3:5 diiodothyroacetic acid.