Arylsulfatases of Human‐Lung Tumors Transplanted into Athymic Mice

Abstract

The activities and properties of arylsulfatases A and B from human lung carcinoma transplanted into athymic mice were demonstrated. The activities of arylsulfatases A and B from transplanted carcinomas with four histological types were more than twofold higher as compared to those from surgical tumors, except for arylsulfatase A activity in blastoma. Arylsulfatase B in transplanted tumors was almost completely replaced, except for blastoma, by an anionic B variant (B₁) which was a minor component of arylsulfatase B in surgical lung tumor and absent in normal human lung. The properties of arylsulfatases A and B from transplanted tumors were essentially identical, respectively, with those from normal lung or surgical tumors in respect of molecular weight, heat stability, pH optimum, isoelectric point (pI), K_m time course profile and substrate specificity. Arylsulfatase B₁ showed the properties similar to B enzyme except for net charge. The cause of the negative charge of tumor B₁ enzyme was investigated. By the action of phosphatase, which was added exogenously or had been persistently included in the partially purified enzyme preparation, B₁ enzyme (pI 7.5) shifted to about pI 8.2. Treatment of B₁ enzyme with neuraminidase, concomitant with the endogenous phosphatase, resulted in marked increase (pI 9.5) of the isoelectric point, identical to that of arylsulfatase B. Thus, it is most probable that tumor B₁ enzyme is modified by additional sialic acid and phosphate bound to arylsulfate B.