SULFATASES 443 



observed with 3 mM /^-glycerophosphate as substrate. The potency of (-(-)- 

 tartrate is not evident in the tabulation since 50% inhibition is produced 

 by 0.07 mM. The failure of lactate to inhibit is surprising, especially as 

 pyruvate is fairly potent. The susceptibility to glucarate observed here has 

 not been observed with Neurospora phosphatase, 12.5 mM having no effect 

 (Kuo and Blumenthal, 1961 ), and Jeffree (1957) found only a moderate inhi- 

 bition {K^= 10 mM) on prostatic phosphatase, it being definitely less potent 

 than oxalate in contrast to the results above. Whether the lactone plays a role 

 in this inhibition is not known. Two anionic polymers have been found to 

 be more potent inhibitors than (-f) -tartrate: polyxenyl phosphate inhibits 

 the Neurospora phosphatase completely at 0.16 mM (Kuo and Blumenthal, 

 1961), and alginate (556 residues) inhibits the prostatic enzyme with a K^ 

 of 0.0054 mM (Jeffree, 1957). These polymer inhibitions are only partially 

 competitive. 



SULFATASES 



Arylsulfatases of type II (liver enzymes A and B and molluscan enzymes) 

 are generally inhibited by sulfate and phosphate, but type I arylsulfatases 

 (liver enzyme C and bacterial enzymes) are resistant. The product inhibi- 

 tion by sulfate was first reported by Tanaka (1938) and shown to be com- 

 petitive with the substrate nitrocatechol sulfate by Roy (1953). The sus- 

 ceptibilities of ox liver arylsulfatases to sulfate vary markedly: The K^ for 

 sulfatase A is 0.75 mM, for sulfatase B is 70 mM, and sulfatase C is not 

 affected (Roy, 1953, 1954 b, 1956). The sulfatase A is inhibited also by 

 several organic sulfates, although not very potently (see accompanying tab- 

 ulation). The following do not inhibit at 25-50 mM: methyl sulfate, glu- 

 cose-3-suLfate, glucose-6-sulfate, and phenyl sulfite. The fact that methyl 

 sulfate does not inhibit and the affinity for the enzyme increases with size 

 of the ring system esterified might indicate that the sulfate group is not 



