Developmental regulation of glucosidase I, an enzyme involved in the processing of asparagine-linked glycoproteins in rat mammary gland

• Published in: The Journal of biological chemistry Vol. 265; no. 17; pp. 9701 - 9706
• Main Authors: SHAILUBHAI, K, SAXENA, E. S, BALAPURE, A. K, VIJAY, I. K
• Format: Journal Article
• Language: English
• Published: Bethesda, MD American Society for Biochemistry and Molecular Biology 15.06.1990
• Subjects: alpha-Glucosidases - isolation & purification; alpha-Glucosidases - metabolism; Animals; Biological and medical sciences; Epidermal Growth Factor - pharmacology; Female; Fundamental and applied biological sciences. Psychology; Hydrocortisone - pharmacology; Insulin - pharmacology; Lactation - metabolism; Mammary Glands, Animal - drug effects; Mammary Glands, Animal - enzymology; Mammary Glands, Animal - physiology; Molecular and cellular biology; Molecular genetics; Molecular Weight; Organ Culture Techniques; Postpartum Period - metabolism; Pregnancy; Pregnancy, Animal - metabolism; Prolactin - pharmacology; Rats; Translation. Translation factors. Protein processing; Hormone; Molecular processing; Purification; Radiolabelling; Rat; Enzyme; Rodentia; Stimulation; Biosynthesis; Glycoproteins; Vertebrata; Immunoprecipitation reaction; Mammalia; Hormonal regulation; Development; Immunoblotting assay; Mammary gland; Biological accumulation
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(19)38727-7

Glucosidase I involved in the processing of N-linked glycoproteins was purified to homogeneity from the lactating rat mammary gland. The purified enzyme exhibited a single band at 85 kDa on 10% sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing conditions. Polyclonal antibodies raised against the enzyme recognized a similar band on Western blots and also inhibited the enzyme activity. The enzyme levels gradually increased until the midlactation stage and thereafter declined sharply during the period of postlactation. A similar profile of the levels of immunoreactive glucosidase I was observed. These findings suggest that the accumulation of glucosidase I is modulated as a function of gland ontogeny. The results on hormonal regulation of glucosidase I indicate that the synthesis of the enzyme is stimulated by a combination of insulin, hydrocortisone, and prolactin; additionally, epidermal growth factor may play a role in this regulation. The above observation was substantiated by immunoprecipitation of [35S]methionine-labeled microsomal extracts with anti-glucosidase I antibodies. The immunoprecipitation of soluble extracts from [35S]methionine-labeled tissue with anti-rat alpha-lactalbumin antibodies indicates that these hormones not only stimulate the synthesis of alpha-lactalbumin but also play an important role in its glycosylation.