Inactivation of Slow Reacting Substance of Anaphylaxis by Human Eosinophil Arylsulfatase

Arylsulfatase preferentially present in the human eosinophil as compared to other leukocytes was isolated by sequential gel filtration and cation exchange chromatography. The apparent molecular weight of 60,000, the preferential cleavage of 4-nitrocatechol sulfate (PNCS) over p-acetyl-benzenesulfonic acid (PABS), inhibition by phosphate ions and pH optimum of 5.7 are characteristics of a type II B arylsulfatase. Eosinophil arylsulfatase inactivated purified human slow reacting substance of anaphylaxis (SRS-A) in a time-dependent reaction with the rate dependent upon the enzyme/substrate ratio. That SRS-A inactivation was the result of intrinsic arylsulfatase activity was indicated by association of PNCS cleavage and SRS-A inactivating activity during chromatography, the similar pH optimum for cleavage of both substrates and the capacity of SRS-A to inhibit PNCS cleavage by arylsulfatase. The finding that eosinophil arylsulfatase inactivates SRS-A suggests that eosinophil ingress into the site of an immediate hypersensitivity reaction in response to ECF-A could represent a regulatory function.