Cystine metabolism

Abstract

In our study of cystine and cystein we have had in mind four different problems,

1. An attempt to synthesize cystine in the animal body either from endogenous nitrogen and sulfur or from these same elements when fed in different forms. This could not be accomplished as has already been shown. 1

2. We prepared several compounds of cystine and cystein 2 where first, the amino group was blocked by some radical such as the phenylacetyl or phenyluramino,—then both the amino group and the carboxyl as in the phenylhydantoin derivative,—then a blocking of the S group with a benzyl radical followed by a blocking of both S-H and amino group, and lastly a blocking of these two and the carboxyl group.

3. We have fed these compounds in order to determine whether the blocking of one or more of these groups prevent the oxidation of the cystine or cystein molecule. Besides this we wished to investigate the reactions by which cystine is apparently converted into cystein, and cystein into cystine in the body.

4. In studying the catabolism of cystine we decided to determine, if possiblle, the origin of the ethereal sulfates.

Lewis 3 has found that the sulfur of phenyluramino cystine is not to any great extent oxidized. He has shown that the compound is however apparently split into phenyluramino cystein, as he obtains a decided test with sodium nitroprusside, and ferric chloride, on the urine of rabbits after feeding the phenyluramino cystine.

Schmidt 4 has shown that taurine, CH. NH².CH².SO³H, is not catabolized in the body but passes out in the urine unchanged. Cysteic acid, CO².HCH.NH.CH².SO³H, only undergoes hydrolytic deamination hut not oxidation in the body.