Studies on the specificity of acetylaminoacyl-peptide hydrolase.
In a continuing attempt to explore the types of specificity determinants that may affect protein-protein (peptide) interactions, a number of short (2-5 residues) acetylated peptides have been compared as substrates for the enzyme acetylaminoacyl-peptide hydrolase (EC 3.4.19.1). The reference substrate was Ac-AAAA, and most of the other substrates were derived from this basic structure by single amino acid substitutions. The Km and kcat for the different substrates were determined by standard steady-state kinetics, and the corresponding delta delta GT++ value derived from kcat/Km was used for the comparison, setting delta detal GT++ for Ac-AAAA equal to 0. The best substrates were found to be those containing negative charges (Asp > Glu) or aromatic residues in positions 1', 2', or 3' (delta delta GT++ values of 2-5 kJ); the negative charge provided by the C-terminus of the substrate also appears to be important, since the amide and O-Me ester derivatives caused a change in delta delta GT++ values of -7 to -8 kJ from the reference peptide. The stimulating effect of the negative charges is consistent with the inhibitory effect of positive charges in similar peptides (Krishna RG, Wold F, 1992, Protein Sci 1:582-589), and the proposed active site model incorporates subsites for both charge-charge and hydrophobic interactions. In assessing all the data, it is clear that the properties of the individual substrates reflect the total make-up of each peptide and not only the effect of a single residue in a given position.(ABSTRACT TRUNCATED AT 250 WORDS)
Sokolik
C W
CW
Department of Biochemistry and Molecular Biology, University of Texas Medical School, Houston 77225.
Liang
T C
TC
Wold
F
F
D000107:Acetylation; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D004563:Electrochemistry; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009132:Muscles / Q000201:enzymology; D009842:Oligopeptides / Q000737:chemistry / Q000378:metabolism*; D010447:Peptide Hydrolases / Q000737:chemistry / Q000378:metabolism*; D011817:Rabbits; D013379:Substrate Specificity; D013816:Thermodynamics
D009842:Oligopeptides; D010447:Peptide Hydrolases; C038220:acylaminoacyl-peptidase