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J. Biol. Chem., Vol. 276, Issue 2, 1152-1155, January 12, 2001
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From the Recombinant rat insulysin was shown to cleave the
internally quenched fluorogenic peptide
2-aminobenzyl-GGFLRKVGQ-ethylenediamine-2,4-dinitrophenol at the R-K
bond, exhibiting a Km of 13 µM and a
Vmax of 2.6 µmol min
Analysis of the Subsite Specificity of Rat Insulysin Using
Fluorogenic Peptide Substrates*
,
,
Department of Biochemistry, University of
Kentucky, Lexington, Kentucky 40536-0084, ¶ Mass Spectrometry
Facility, University of Kentucky, Lexington, Kentucky
40506-0286, and the § Department of Biophysics,
Escola Paulista de Medicina, Sao Paulo 04034, Brazil
1
mg
1. Derivatives of this peptide in which the
P2 leucine or the P2' valine were replaced
with other residues were used to probe the subsite specificity of the
enzyme. Varying the P2 residue produced a 4-fold range in
Km and a 7-fold range in
kcat. The nature of the P2 residue
had a significant effect on the site of cleavage. Leucine, isoleucine,
valine, and aspartate produced cleavage at the R-K bond. Asparagine
produced 36% cleavage at the N-R bond and 64% cleavage at the R-K
bond, whereas with alanine or serine the A-R and S-R bonds were the
major cleavage sites. With tyrosine, phenylalanine, methionine, or
histidine representing the varied residue X, cleavages at
F-X, X-R, and R-K were seen, whereas with
tryptophan equal cleavage occurred at the F-W and W-R bonds. Variable
P2' residues produce less of a change in both Km and kcat and have little
influence on the cleavage site. Exceptions are phenylalanine,
tyrosine, leucine, and isoleucine, which in addition to producing
cleavage at the R-K bond, produce significant cleavage at the L-R
bond. Alanine and tyrosine were unique in producing cleavage at the
F-L bond. Taken together, these data suggest that insulysin
specificity is directed toward the amino side of hydrophobic and basic
residues and that the enzyme has an extended substrate binding site.
*
This work was supported in part by National Institute on
Drug Abuse Grants DA02243 and DA 07062.The costs of publication of this
article were defrayed in part by the
payment of page charges. The article
must therefore be hereby marked
"advertisement" in accordance with 18 U.S.C. Section
1734 solely to indicate this fact.
To whom correspondence should be addressed: Dept. of
Biochemistry, College of Medicine, Chandler Medical Center, University of Kentucky, 800 Rose St., Lexington, KY 40536-0084. Tel.:
859-323-5549; Fax: 859-323-1727; E-mail: lhersh@pop.uky.edu.
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