A variant form of arylsulfatase A in human urine derived directly from the renal pelvis: kinetic and immunological characterization.
Arylsulfatase A (aryl-sulfate sulfohydrolase, EC 3.1.6.1) was examined in voided and in nephrostomic urine. A variant form of the enzyme was found in nephrostomic urine, in addition to the minor form, which is the sole component of arylsulfatase A in voided urine. The nephrostomic enzyme differed from the voided urine enzyme with respect to the kinetic parameters, the isoelectric point, heat stability and immunological reactivity. The isoelectric points of the voided urine and nephrostomic enzymes were 4.7 and 5.3, respectively. The nephrostomic enzyme was more heat-labile at 62.5 degrees C than the voided urine enzyme. Although the Km values of the two enzymes with nitrocatechol sulfate as substrate were almost the same, the V value of the nephrostomic enzyme was approx. one-hundredth that of the voided urine enzyme. The molecular weight (almost 130 000) did not differ between the voided urine and nephrostomic enzymes. It was demonstrated by various methods, using IgG antibody against the purified voided urine enzyme, that the nephrostomic enzyme was antigenically distinct from the voided urine enzyme.