The Hunter Corrective Factor

Fibroblasts from patients with the syndrome are deficient in a specific protein, designated Hunter corrective factor, which is required for the degradation of sulfated mucopolysaccharide. This factor has now been purified 120-fold from normal human urine by (NH4)2SO4 fractionation, gel chromatography on Sephadex G-200, passage through anti-albumin Sepharose to remove albumin, a major contaminant, and finally, preparative polyacrylamide gel electrophoresis. The last procedure separates two isofactors, which are probably charge isomers; both differ in charge from the factor derived from fibroblast secretions. The molecular weight of urinary factor is estimated at 65,000 by polyacrylamide gel electrophoresis and 114,000 by gel filtration. The most highly purified preparation of urinary factor shows a single protein component in polyacrylamide gel electrophoresis at pH 8, but can be resolved into several bands by isoelectric focusing in polyacrylamide gel. It is free of the common lysosomal glycosidases and sulfatases, as well as of factors effective in other mucopolysaccharidoses (Hurler, Scheie, Sanfilippo A and B, and Maroteaux-Lamy). The corrective factor accelerates the degradation, by fibroblasts, of dermatan sulfate labeled in the sulfate or galactosamine moieties, as well as of exogenously added proteodermatan [35S]sulfate. The effect of the factor persists in the recipient cells with a half-life of 2 days.