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Leucine transport in brush border membrane vesicles from freshwater insect larvae
Author(s) -
Forcella Matilde,
Berra Elisa,
Giacchini Roberto,
Parenti Paolo
Publication year - 2006
Publication title -
archives of insect biochemistry and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.576
H-Index - 66
eISSN - 1520-6327
pISSN - 0739-4462
DOI - 10.1002/arch.20147
Subject(s) - hydropsychidae , biology , sodium , leucine , brush border , vesicle , larva , amino acid , chemistry , botany , biochemistry , membrane , organic chemistry
Leucine transport across brush border membrane vesicles prepared from four insect species common to European freshwater streams has been characterized. The species studied were: Ephemera danica (Ephemeroptera: Ephemeridae), Isoperla grammatica (Plecoptera: Perlodidae), Hydropsyche pellucidula (Trichoptera: Hydropsychidae), and Hybomitra bimaculata (Diptera: Tabanidae). The transport differed among the studied taxa for several features, including pH and sodium dependence, substrate affinity and specificity, and efficiency. In H. pellucidula and E. danica , leucine uptake was higher at pH 7.4 than at more alkaline or acidic pH values, whereas in I. grammatica and H. bimaculata , the uptake was rather constant when pH varied from 5.0 to 7.4, then strongly decreased at pH 8.8. All but E. danica displayed a transient intravescicular leucine accumulation in the presence of sodium, suggesting the existence of a cation‐leucine symport mechanism. The sodium dependence ranged according to the following order: H. pellucidula > I. grammatica > H. bimaculata > E. danica . Moreover, in H. pellucidula and I. grammatica , the sodium‐dependence was stronger at pH 8.8 than at pH 7.4. In E. danica , leucine uptake was sodium‐independent at all pH values. The highest value of V max (45.3 pmol·s –1 ·mg proteins –1 ) was in E. danica , which, however, displayed the lowest affinity ( K m 137 μM) when compared to the kinetic parameters of other taxa. The V max and K m values were: 40 and 52.5, 32.1 and 12.5, and 4.5 and 230 for H. bimaculata , H. pellucidula , and I. grammatica , respectively. The obtained results are discussed within our current knowledge of amino acid transport systems in insects. Arch. Insect Biochem. Physiol. 63:110–122, 2006. © 2006 Wiley‐Liss, Inc.