Enzymatic phosphorylation of lysosomal enzymes in the presence of UDP-N-acetylglucosamine. Absence of the activity in I-cell fibroblasts

Summary: Recent finding of a-N-ocetylglucosamine( I)phospho(6)mannose diesters in lysosomal enzymes suggested that formation of monnose 6-phosphate residues involves transfer of N-acetylglucosamine l- hos hote to mannose. Using dephosphorylated R-hexosaminidase as acceptor and F t3-3 “I P UDP-N-acetylglucosamine OS donor for the phosphate group, phosphorylation of R-hexosaminidose by microsomes from rot liver, humon placenta and human skin fibroblosts wos achieved. The reaction was not affected by tunicomycin. Acid hydrolysis released monnose 6-[32P] phosphate from the phosphorylated l3-hexosaminidase. Our results suggest that lysosomal enzymes are phosphorylated by tronsfer of N-acetylglucosamine l-phosphate from UDP-N-ocetylglucosamine. The transferose activity wos deficient in fibroblasts from patients affected with l-cell disease. This deficiency is proposed to be the primary enzyme defect in I-ccl I disease.