Protein specific N-glycosylation of tyrosinase and tyrosinase-related protein-1 in B16 mouse melanoma cells.

Abstract

Tyrosinase and tyrosinase-related protein-1 (TRP-1) are two melanogenic enzymes that regulate melanin biosynthesis. Both are glycoproteins and belong to the TRP-1 gene family. They share a significant level of sequence similarity in several regions, including the catalytic domain and the potential N-glycosylation sites. We have recently shown that inhibition of the early steps of N-glycan processing in B16F1 cells dramatically affects tyrosinase activity and melanin synthesis. We present here results on N-glycan processing of TRP-1 and tyrosinase and compare the maturation process and activity of both glycoproteins in the presence of inhibitors of the endoplasmic reticulum stages of N-glycosylation. N-glycan analysis reveals that each of these two glycoproteins contains a mixture of high-mannose and sialylated complex N-glycans. However, in contrast to TRP-1, tyrosinase presents a homogeneous high-mannose glycoform, also. In the presence of alpha-glucosidases inhibitors, the maturation of tyrosinase N-glycans is completely inhibited, whereas TRP-1 is still able to acquire some complex glycans, indicating that endomannosidase acts preferentially on the later glycoprotein. In addition, the dopa-oxidase activity of tyrosinase is totally abolished, whereas for TRP-1 it is only partially affected. The results suggest that despite their structural similarity, tyrosinase is more sensitive than TRP-1 to perturbations of early N-glycan processing, in terms of maturation and catalytical activity.

• Authors: G Negroiu, N Branza-Nichita, A J Petrescu, R A Dwek, S M Petrescu
• Journal: The Biochemical journal (Biochem J) Vol. 344 Pt 3 Pg. 659-65 (Dec 15 1999) ISSN: 0264-6021 [Print] England
• PMID: 10585852 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Membrane Glycoproteins
• Oligosaccharides
• Polysaccharides
• Proteins
• 1-Deoxynojirimycin
• miglustat
• Oxidoreductases
• Tyrp1 protein, mouse
• tyrosinase-related protein-1
• Monophenol Monooxygenase
• Glycoside Hydrolases
• Hexosaminidases
• Amidohydrolases
• Peptide-N4-(N-acetyl-beta-glucosaminyl) Asparagine Amidase

Topics

• 1-Deoxynojirimycin (analogs & derivatives, pharmacology)
• Amidohydrolases (metabolism)
• Animals
• Glycoside Hydrolases (antagonists & inhibitors, metabolism)
• Glycosylation
• Hexosaminidases (metabolism)
• Membrane Glycoproteins
• Mice
• Monophenol Monooxygenase (metabolism)
• Oligosaccharides (analysis)
• Oxidoreductases
• Peptide-N4-(N-acetyl-beta-glucosaminyl) Asparagine Amidase
• Polysaccharides (chemistry)
• Proteins (metabolism)
• Tumor Cells, Cultured