Chymotryptic specificity determinants in the 1.0 A structure of the zinc-inhibited human tissue kallikrein 7.
hK7 or human stratum corneum chymotryptic enzyme belongs to the human tissue kallikrein (hKs) serine proteinase family and is strongly expressed in the upper layers of the epidermis. It participates in skin desquamation but is also implicated in diverse skin diseases and is a potential biomarker of ovarian cancer. We have solved x-ray structures of recombinant active hK7 at medium and atomic resolution in the presence of the inhibitors succinyl-Ala-Ala-Pro-Phe-chloromethyl ketone and Ala-Ala-Phe-chloromethyl ketone. The most distinguishing features of hK7 are the short 70-80 loop and the unique S1 pocket, which prefers P1 Tyr residues, as shown by kinetic data. Similar to several other kallikreins, the enzyme activity is inhibited by Zn(2+) and Cu(2+) at low micromolar concentrations. Biochemical analyses of the mutants H99A and H41F confirm that only the metal-binding site at His(99) close to the catalytic triad accounts for the noncompetitive Zn(2+) inhibition type. Additionally, hK7 exhibits large positively charged surface patches, representing putative exosites for prime side substrate recognition.
Debela
Mekdes
M
Max-Planck-Institut für Biochemie, Proteinase Research Group, Am Klopferspitz 18, 82152 Martinsried, Germany.
Hess
Petra
P
Magdolen
Viktor
V
Schechter
Norman M
NM
Steiner
Thomas
T
Huber
Robert
R
Bode
Wolfram
W
Goettig
Peter
P
D000595:Amino Acid Sequence; D020134:Catalytic Domain; D002918:Chymotrypsin / Q000737:chemistry* / Q000378:metabolism; D003300:Copper / Q000494:pharmacology; D018360:Crystallography, X-Ray; D006801:Humans; D066298:In Vitro Techniques; D007610:Kallikreins / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D015842:Serine Proteinase Inhibitors / Q000494:pharmacology; D055672:Static Electricity; D013379:Substrate Specificity; D015032:Zinc / Q000494:pharmacology
D011994:Recombinant Proteins; D015842:Serine Proteinase Inhibitors; D003300:Copper; C082472:KLK7 protein, human; D007610:Kallikreins; D002918:Chymotrypsin; D015032:Zinc