Urinary free and conjugated 5-S-cysteinyldopa in normal subjects and in patients with melanoma.

We measured free and total 5-S-cysteinyldopa excretion in 24-h urine specimens from nine patients with malignant melanoma and forty-five controls, and found that the levels of 5-S-cysteinyldopa excretion (measured by a fluorometric method) were greatly increased in the melanoma patients. The conjugates were hydrolysed by enzymatic treatment with beta-glucuronidase/arylsulphatase, and we found that the percentage of conjugated 5-S-cysteinyldopa was higher in urines with a low content of free 5-S-cysteinyldopa than in those with a higher concentration.