Genetically defined peptidases of maize. I. Biochemical characterization of allelic and nonallelic forms.
A number of biochemical properties have been investigated for both allelic and nonallelic forms of maize peptidases. Four aminopeptidases exist in maize (LAP-A, LAP-B, LAP-C, and LAP-D) and are the products of four diallelic loci. The aminopeptidases fall into two biochemical groups on the basis of these studies. LAP-A and LAP-D have comparatively low apparent Km (Kapp) values for arginine-naphthylamide derivatives and high velocities for arginine-naphthyl-amide and lysine-naphthylamide. LAP-B and LAP-C, on the other hand, have lower Kapp values for leucine-naphthylamide and higher velocities for nonpolar amino acid-naphthylamides than for arginine-naphthylamide. LAP-A and LAP-D are also relatively more heat stable than LAP-B and LAP-C and have somewhat higher molecular weights (71,500) than LAP-B and LAP-C (63,500). In determining molecular weights of the peptidases, use was made of their differential substrate specificities toward amino acid-naphthylamides. Some properties of genetically defined maize endopeptidase are also presented. Maize endopeptidase is inhibited by the sulfhydryl reagents N-ethylmaleimide and p-chloromercuribenzoate (pCMB), and by tosyl lysine chloromethyl ketone, Maize aminopeptidase activity is inhibited by N-ethylmaleimide, pCMB, and EDTA (ethylenediamine tetraacetic acid).
D000483:Alleles; D000626:Aminopeptidases / Q000302:isolation & purification / Q000378:metabolism; D004355:Drug Stability; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D007527:Isoenzymes / Q000302:isolation & purification / Q000378:metabolism; D007700:Kinetics; D008970:Molecular Weight; D010447:Peptide Hydrolases / Q000302:isolation & purification / Q000378:metabolism*; D010944:Plants / Q000201:enzymology*; D003313:Zea mays / Q000201:enzymology
D007527:Isoenzymes; D010447:Peptide Hydrolases; D000626:Aminopeptidases