期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1978
卷号：75
期号：4
页码：1750-1753
DOI：10.1073/pnas.75.4.1750
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Highly purified fractions of gamma-glutamyl transpeptidase [gamma-glutamyltrinsferase; (5-glutamyl)-peptide:amino-acid 5-glutamyltransferase, EC 2.3.2.2 ] from normal and malignant rat mammary tissue were prepared. Analyses by isoelectric focusing indicate the existence of at least 12 enzymatically active species. The gamma-glutamyl transpeptidase from the tumor tissue had a greater proportion of the activity concentrated in the more negative species than the enzyme from normal tissue. Treatment of the two enzyme preparations with neuraminidase (acylneuraminyl hydrolase, EC 3.2.1.18 ) greatly reduced this difference. When whole tissue homogenates were treated with papain to solubilize the enzyme and then focused, the same relationship held. The neuraminidase activities in the two homogenates were similar, but the sialytransferase activity (CMP-N-acetylneuraminate:D-galactosyl-glycoprotein N-acetylneuraminyltransferase, EC 2.4.99.1 ) of the tumor homogenate was 13 times that of the normal mammary homogenate. These observations suggest that the gamma-glutamyl transpeptidase of the tumor is more heavily sialylated than that from the normal tissue, possibly reflecting the greater sialyltransferase activity of the tumor.
