The activity of arylsulfatase A and B on tyrosine O-sulfates

Abstract

l-Tyrosine O-sulfate was hydrolyzed by pure human arylsulfatase A (aryl-sulfate sulfohydrolase, EC 3.1.6.1). The rate of hydrolysis was 1 20 of the rate with nitrocatechol sulfate, but was comparable to the rate with cerebroside sulfate. The reaction was optimal at pH 5.3–5.5 and displayed zero order kinetics with time and enzyme concentration. The K m was about 35 mM. The enzyme showed no stereospecificity and hydrolyzed D-tyrosine O-sulfate with K m and V sinmilar to those for the L-isomer. Arylsulfatase B was less than 5% as effective as arylsulfatase A in catalyzing the hydrolysis of the tyrosine sulfates. The daily urinary excretion of tyrosine sulfate by a patient with metachromatic leukodystrophy (arylsulfatase A deficiency) was comparable to the excretion by control subjects. The biological relevance of the tyrosine sulfatase activity of arylsulfatase A remains uncertain.