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Peptide-Bound Methionine Can Be a Source of Methionine for the Synthesis of Secreted Proteins by Mammary Tissue Explants from Lactating Mice^1,2,3,

Shiping Wang^*, Kenneth E. Webb, Jr.^*,4 and Michael R. Akers

^* Department of Animal and Poultry Sciences Department of Dairy Science, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061

Mammary tissue explants from d 10–11 of lactating CD-1 mice were used to study the ability of methionine-containing di- to octapeptides to substitute for free methionine for the synthesis of secreted proteins. Explants were incubated in a medium containing ³H-leucine and either L-methionine or one of 23 methionine-containing peptides. The ability of methionine substrates to promote incorporation of ³H-leucine into secreted proteins was quantified. Mammary tissue explants were able to utilize methionine from all peptides tested. All of the peptides were at least as effective as free methionine in promoting ³H-leucine incorporation into secreted proteins. Most di- and tripeptides promoted 15–76% greater (P < 0.05) ³H-leucine incorporation than did free methionine. There was a negative correlation (r = -0.89, P < 0.01) between the rate of ³H-leucine incorporation promoted by peptides and the number of amino acid residues in the peptides. The incorporation of ³H-leucine promoted by some dipeptides was reduced (P < 0.05) in the presence of a 200-fold higher concentration of glycylsarcosine or carnosine. The results indicate that peptide-bound methionine can serve as a source of methionine for the synthesis of secreted proteins by lactating mammary tissue. Mediated transport of some peptides is probably involved in peptide utilization.

KEY WORDS: • amino acids • tissue culture • peptides • mammary • mice

¹ Presented in part at Experimental Biology '93, March 1993, New Orleans, LA [Wang, S., Webb, K. E., Jr. & Akers, R. M. (1993) Methionine from peptides can be used by mammary tissue explants from lactating mice for the synthesis of secreted proteins. FASEB J. 7: A522 (abs.)].

² Supported in part by the John Lee Pratt Animal Nutrition Program of Virginia Polytechnic Institute and State University. Support was also provided by the Virginia Agriculture Experiment Station and the Cooperative State Research Service, U.S. Department of Agriculture under Project No. 6129990.

³ The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 USC section 1734 solely to indicate this fact.

⁴ To whom correspondence should be addressed.

Manuscript received 23 August 1995. Revision accepted 23 February 1996.

This article has been cited by other articles:

				E. R. Gilbert, E. A. Wong, and K. E. Webb Jr. BOARD-INVITED REVIEW: Peptide absorption and utilization: Implications for animal nutrition and health J Anim Sci, September 1, 2008; 86(9): 2135 - 2155. [Abstract] [Full Text] [PDF]