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  • Cysteamine depletes cystinotic leucocyte granular fractions of cystine by the mechanism of disulphide interchange.

Cysteamine depletes cystinotic leucocyte granular fractions of cystine by the mechanism of disulphide interchange.

The Biochemical journal (1985-06-15)
W A Gahl, F Tietze, J D Butler, J D Schulman
ABSTRACT

Cystinotic lysosome-rich leucocyte granular fractions, loaded with [35S]cystine, were exposed to different cystine-depleting agents. During a 30 min incubation at 37 degrees C, untreated cystinotic granular fractions lost negligible [35S]cystine when corrected for lysosome rupture. Granular fractions exposed to 0.1 mM-cysteamine lost 64% of their initial cystine, and hexosaminidase activity was decreased by 10%. This was accompanied by the formation of high concentrations of [35S]cysteine-cysteamine mixed disulphide within the granular-fraction pellet, and, in the presence of N-ethylmaleimide, increasing amounts of [35S]cysteine-N-ethylmaleimide adduct outside the granular fraction. In separate experiments, [35S]cystine exited cystinotic leucocyte lysosomes at a negligible rate (half-times 199 and 293 min), but [35S]cysteine-cysteamine mixed disulphide exhibited substantial egress (half-times 66 and 88 min) and was recovered intact outside the granular-fraction pellet. We conclude that cysteamine depletes lysosomes of cystine by participating in a thiol-disulphide interchange reaction to produce cysteine and cysteine-cysteamine mixed disulphide, both of which traverse the cystinotic leucocyte lysosomal membrane.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Cysteamine, ≥98.0% (RT)