Amino acid and carbohydrate composition of a lysosomal cysteine proteinase from Trypanosoma cruzi. Absence of phosphorylated mannose residues.
The size of a lysosomal cysteine proteinase from epimastigotes of Trypanosoma cruzi decreased from 60 to 54 kDa upon treatment with endo beta-N-acetylglucosaminidase H. A lower-molecular weight component (30-35 kDa), which usually accompanies the 60-kDa protein also increased its electrophoretic mobility, and seems to consist of a mixture of degradation products of the enzyme, since both the larger and the smaller components had the same N-terminal sequence as the 60-kDa protein. The amino acid composition of the protein moiety and the composition of the oligosaccharide chains have been determined. The oligosaccharide chains are of the high-mannose type, and contain 6, 7, 8 or 9 mannose residues, as shown both by in vivo labeling with [U-14C]glucose, and by labeling the endo-beta-N-acetylglucosaminidase H-sensitive oligosaccharides of the purified enzyme with tritiated sodium borohydride. The oligosaccharide chains did not contain phosphate residues. Further studies with [U-14C]-labeled total glycoproteins of T. cruzi and enzyme assays, suggest that T. cruzi and other trypanosomatids do not target their lysosomal enzymes to the organelle through the mannose-6-phosphate marker pathway.
Cazzulo
J J
JJ
Instituto de Investigaciones Bioquímicas Fundación Campomar, Facultad de Ciencias Exactas y Naturates, Universidad de Buenos Aires-CONICET, Argentina.
Hellman
U
U
Couso
R
R
Parodi
A J
AJ
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002240:Carbohydrate Sequence; D002241:Carbohydrates / Q000032:analysis; D003546:Cysteine Endopeptidases / Q000302:isolation & purification; D008247:Lysosomes / Q000201:enzymology*; D008360:Mannosephosphates / Q000032:analysis; D008969:Molecular Sequence Data; D008970:Molecular Weight; D014349:Trypanosoma cruzi / Q000201:enzymology*
D000596:Amino Acids; D002241:Carbohydrates; D008360:Mannosephosphates; D003546:Cysteine Endopeptidases