JDS
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

Journal of Dairy Science Vol. 80 No. 12 3241-3248
© 1997 by American Dairy Science Association ®
This Article
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Basch, J. J.
Right arrow Articles by Farrell, H. M.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Basch, J. J.
Right arrow Articles by Farrell, H. M., Jr.

Arginase in Lactating Bovine Mammary Glands: Implications in Proline Synthesis

J. J. Basch 1, E. D. Wickham 1, and H. M. Farrell Jr. 1

1 Dairy Products Research Unit, US Department of Agriculture, Eastern Regional Research Center, Agricultural Research Service, 600 E. Mermaid Lane, Wyndmoor, PA 19038

The occurrence and subcellular distribution of arginase have been studied in mammary glands from lactating dairy cattle. The enzyme appears to be localized in the mitochondrial fraction, although a significant amount has been found to be associated with the cytosolic fraction. Both mitochondrial and cytosolic arginase are activated by heating with Mn2+. The Michaelis constants for the two fractions, however, are different: 49.5 and 18.5 mM for the mitochondrial fraction and cytosolic fraction, respectively. Overall, the total enzyme concentration in the gland suggests that these enzymes contribute to the conversion of arginine to ornithine. Ornithine, in turn, may be converted by ornithine aminotransferase into an intermediate, L-Delta1-pyrroline-5-carboxylate; concurrently, alpha-keto-glutarate is transformed into glutamic acid. Finally, pyrroline-5-carboxylate reductase yields proline, an important amino acid that is needed for casein synthesis. Because pyrroline-5-carboxylate reductase requires NADPH, and because ornithine aminotransferase uses alpha-ketoglutarate, this new pathway is linked to the Krebs cycle through the cytosolic isocitrate dehydrogenase, which is the source of both of these intermediates.

Key Words: milk secretion • enzymes • proline

Submitted on September 19, 1996
Accepted on June 23, 1997




This article has been cited by other articles:


Home page
 Proc. Natl. Acad. Sci. USAHome page
S. A. Maxwell and G. E. Davis
Differential gene expression in p53-mediated apoptosis-resistant vs. apoptosis-sensitive tumor cell lines
PNAS, November 21, 2000; 97(24): 13009 - 13014.
[Abstract] [Full Text] [PDF]


HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Copyright © 1997 by the American Dairy Science Association ®.