title: Activation of the herpes simplex virus type 1 protease.
abstract: The catalytic efficiency of the mature HSV-1 protease has been examined as a function of solvent composition. With the peptide substrate HTYLQASEKFKMWG-amide, the specificity constant (kcat/Km) at pH 7.5 for cleavage is 5.2 M-1 s-1. This value increases to 38 M-1 s-1 when 25% glycerol is present in the reaction mixture. It was found that glycerol activation is but one case of the general phenomenon of HSV-1 protease activation by kosmotropes, or water structure-forming cosolvents. For example, an 860-fold increase in the protease activity (kcat/Km = 4500 M-1 s-1) occurs in the presence of 0.8 M sodium citrate. Similarly, the presence of 0.8 M sodium phosphate activates the catalytic efficiency by 420-fold (kcat/Km = 2200 M-1 s-1). The extent of HSV-1 protease activation by various anions correlates with the Hofmeister series. Both the susceptibility to proteolysis by trypsin and the protein fluorescence spectra of the HSV-1 protease change in the presence of activating solvents, suggesting a conformational change accompanying activation.
authors.affiliation: Department of Biological Chemistry, Merck Research Laboratories, West Point, Pennsylvania 19486, USA.
authors.forename: D L
authors.initials: DL
authors.lastname: Hall
authors.forename: P L
authors.initials: PL
authors.lastname: Darke
mesh_terms: D000595:Amino Acid Sequence; D000838:Anions / Q000494:pharmacology; D010450:Endopeptidases / Q000302:isolation & purification / Q000378:metabolism*; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018259:Herpesvirus 1, Human / Q000201:enzymology*; D007700:Kinetics; D008969:Molecular Sequence Data; D009711:Nucleotides / Q000494:pharmacology; D010455:Peptides / Q000737:chemistry; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000378:metabolism; D012697:Serine Endopeptidases / Q000302:isolation & purification / Q000378:metabolism*; D012997:Solvents / Q000494:pharmacology; D013050:Spectrometry, Fluorescence; D013379:Substrate Specificity; D014764:Viral Proteins
chemical_list: D000838:Anions; D004791:Enzyme Inhibitors; D009711:Nucleotides; D010455:Peptides; D011994:Recombinant Proteins; D012997:Solvents; D014764:Viral Proteins; C079287:scaffold protein, Herpes simplex virus-1; D010450:Endopeptidases; D012697:Serine Endopeptidases