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Published 2005

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Publication details

Journal : Journal of Experimental Biology , vol. 208 , p. 2885–2894 , 2005

International Standard Numbers :
Printed : 0022-0949
Electronic : 1477-9145

Publication type : Academic article

Contributors : Dabrowski, Konrad; Terjesen, Bendik Fyhn; Zhang, Yongfang; Phang, JM; Lee, Kyeong-Jun

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Kjetil Aune
Chief Librarian


The premise that a dietary dipeptide approach will
improve the understanding of amino acid utilization in the
fastest-growing vertebrate, the teleost fish, was tested by
examining the muscle free amino acid (FAA) pool and
enzyme activities, in concert with growth response, when
dietary amino acids were provided in free, dipeptide or
protein molecular forms. We present the first evidence in
fish that, in response to a synthetic dipeptide diet, muscle
FAA varies as a result of both growth rate and amino acid
availability of specific peptides. We demonstrate
significantly diminished muscle indispensable FAA (3–10-
fold) in rainbow trout alevins fed a dipeptide-based diet
compared with a protein-based diet. The dipeptide-based
diet did not contain proline, resulting in 10–27-fold less
muscle free proline and hydroxyproline in alevins. The
response of alevins fed FAA-based or peptide-based diets
can be indicative of collagen turnover (Hyp/Pro ratio) and
showed significant differences between dietary treatments.
Pyrroline-5-carboxylate (P5C) reductase activity was
detected, suggesting that P5C may ameliorate proline
deficiency, but synthesis from glutamate could not
maintain free proline levels in muscle. This finding will
provide an impetus to test whether proline is conditionally
indispensable in young fish, as in mammals and birds.
This study shows that amino acids given entirely as
dipeptides can sustain fish growth, result in muscle FAA
and enzyme responses in line with dietary levels and
identify growth-limiting amino acids. The understanding
of these factors necessitates a diet formulation that will
improve the accuracy of determining amino acid
requirements in the early life stages of vertebrates.