Year of Publication

2009

Paper Type

Master's Thesis

College

College of Arts and Sciences

Degree Name

Master of Arts in Biology (MA)

Department

Biology

First Advisor

Dr. Greg Ahearn

Second Advisor

Dr. Doria Bowers

Third Advisor

Dr. George Gerencser

Department Chair

Dr. Daniel C. Moon

College Dean

Dr. Barbara Hetrick

Abstract

The current study is a characterization of L-leucine absorption across the American lobster intestine in order to determine the likelihood of a bis-complex formation with zinc ([Leu]-Zn-[Leu]) as a possible substrate for PEPT1. This study required isolated lobster intestines to be mounted in a perfusion chamber in order to quantify 3H-L-leucine transport. It was hypothesized that an apical dipeptide transporter, PEPT1, was responsible for uptake of L-leucine via formation of a bis-complex with zinc ([Leu]-Zn-[Leu]) in the form of molecular mimicry, where the bis-complex mimics the normal dipeptide substrate of the proposed carrier system. It was found that L-leucine transport across the lobster intestine was significantly stimulated by luminal zinc and other cations and that this stimulation led to enhanced net flux of the amino acid across the intestine compared to its net flux in the absence of these cations. Transmural transport ofL-leucine was also significantly stimulated by a variety of organic solutes including L-histidine, L-cysteine, and glycylsarcosine (GLY-SAR) by way of countertransport. While many observations in the present study suggest that PEPT1 may be the carrier system responsible for transmural leucine transport in the presence of zinc, other cation-dependent carrier systems, such as the B^0 transporter, with strong transstimulation properties, may also be a suitable candidate for leucine transport in the lobster intestine.

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