Synthesis and Evaluation of Alternative Substrates for Arginase

Bioorg Chem. 2002 Apr;30(2):81-94. doi: 10.1006/bioo.2001.1228.

Abstract

Two novel carboxyl-containing arginase substrates, 4-guanidino-3-nitrobenzoic acid and 4-guanidino-2-nitrophenylacetic acid, have been synthesized and found to give enhanced catalysis and dramatically lower K(m) values relative to 1-nitro-3-guanidinobenzene, a substrate designed for use in a chromophoric arginase assay. To more efficiently mimic the natural substrate, a series of sulfur analogs of L-arginine were synthesized and kinetically characterized. The parent compound, L-thioarginine, with the bridging guanidinium nitrogen of L-arginine replaced with sulfur, functions as efficiently as the natural substrate. The desamino analog shows extremely low turnover, while the k(cat) of the descarboxy analog is only 75-fold lower than that of arginine. These results suggest that the bridging nitrogen of L-arginine is not important for either substrate binding or catalysis, while the alpha-carboxyl group facilitates substrate binding, and the alpha-amino group is necessary for efficient catalysis. Isothiourea homologs previously reported to be nitric oxide synthase inhibitors have been found to undergo a rapid non-enzymatic rearrangement to a species that is probably the true inhibitor.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Arginase / chemistry
  • Arginase / metabolism*
  • Arginine / analogs & derivatives*
  • Arginine / chemical synthesis
  • Arginine / chemistry
  • Arginine / metabolism
  • Benzoates / chemical synthesis
  • Benzoates / chemistry
  • Benzoates / metabolism
  • Chromogenic Compounds
  • Fluorescent Dyes
  • Guanidines / chemistry
  • Guanidines / metabolism
  • Kinetics
  • Liver / enzymology
  • Nitrobenzenes / chemistry
  • Nitrobenzenes / metabolism
  • Nitrophenols / chemical synthesis
  • Nitrophenols / chemistry
  • Nitrophenols / metabolism
  • Rats
  • Substrate Specificity
  • Thiourea / chemistry

Substances

  • 1-nitro-3-guanidinobenzene
  • Benzoates
  • Chromogenic Compounds
  • Fluorescent Dyes
  • Guanidines
  • Nitrobenzenes
  • Nitrophenols
  • thioarginine
  • Arginine
  • Arginase
  • Thiourea