Developmental regulation of glucosidase I, an enzyme involved in the processing of asparagine-linked glycoproteins in rat mammary gland.
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.
Department of Animal Sciences, University of Maryland, College Park 20742.
K
K
Shailubhai
E S
ES
Saxena
A K
AK
Balapure
I K
IK
Vijay
D000818:Animals; D004815:Epidermal Growth Factor / Q000494:pharmacology; D005260:Female; D006854:Hydrocortisone / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology; D007774:Lactation / Q000378:metabolism*; D008321:Mammary Glands, Animal / Q000187:drug effects / Q000201:enzymology* / Q000502:physiology; D008970:Molecular Weight; D009924:Organ Culture Techniques; D049590:Postpartum Period / Q000378:metabolism*; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000378:metabolism*; D011388:Prolactin / Q000494:pharmacology; D051381:Rats; D000520:alpha-Glucosidases / Q000302:isolation & purification / Q000378:metabolism*
D007328:Insulin; D004815:Epidermal Growth Factor; D011388:Prolactin; C042059:glucosidase I; D000520:alpha-Glucosidases; D006854:Hydrocortisone