The Metabolism of S-(2-Carboxy-1-Methylethyl)-L-Cysteine

Abstract

1. Naturally occurring S-alkyl cysteines and their sulphoxides Many S-alkyl cysteines and the corresponding sulphoxides occur naturally, sometimes as the γ-L-glutamyl dipeptides or as S-alkyl glutathiones as well as in the free form. They are particularly abundant in some higher plants; from the onion alone, Virtanen and his co-workers have isolated seven (91). Recently a number of S-alkyl cysteines have been demonstrated in animal urine and tissue. Table I gives a list of naturally occurring S-alkyl cysteines and sources in which they have been demonstrated. The table includes only simple S-alkyl cysteines, S-(carboxyalkyl) cysteines and S-(hydroxyalkyl) cysteines.