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PZ-peptidase from chick embryos. Purification, properties, and action on collagen peptides
Insights
This study purified PZ-peptidase, an enzyme that breaks down collagen fragments. Its activity is specific, suggesting a role in late-stage collagen degradation.
Area of Science:
- Biochemistry
- Enzymology
- Molecular Biology
Background:
- PZ-peptidase is an endopeptidase.
- It cleaves a synthetic substrate (PZ-peptide) used for clostridial collagenase.
- Understanding its function is key to collagen metabolism research.
Purpose of the Study:
- To purify and characterize PZ-peptidase from chicken embryos.
- To determine its enzymatic properties and substrate specificity.
- To elucidate its potential role in collagen breakdown.
Main Methods:
- Purification of PZ-peptidase to homogeneity from chicken embryos.
- Enzyme kinetics assays to determine kinetic parameters (Km, Vmax).
- Inhibition studies using various chemical agents and metal ions.
- Substrate specificity analysis using diverse proteins and collagen peptides.
Main Results:
- PZ-peptidase has a molecular weight of 77,000, pH optimum of 7.5-8.5, and isoelectric point of 5.0.
- Kinetic parameters: Km = 2 X 10(-4) M, Vmax = 4.2 mumol/min/mg.
- Activity is enhanced by reducing agents and divalent cations (Ca2+, Sr2+, Mg2+); inhibited by p-hydroxymercuribenzoate and N-ethylmaleimide.
- Shows specific activity on collagen peptides, particularly the Hyp--Gly bond in alpha1(II)-CB6-C2, suggesting a role in late-stage collagen degradation.
Conclusions:
- PZ-peptidase is a distinct enzyme with specific collagenolytic activity.
- Its substrate specificity suggests a role in breaking down collagen fragments into smaller peptides (5-30 residues).
- Further research can explore its physiological significance in connective tissue remodeling and turnover.
Abstract:
PZ-peptidase is an endopeptidase that cleaves the synthetic substrate developed for clostridial collagenase, 4-phenylazobenzyloxycarbonyl-L-Pro-L-Leu-Gly-L-Pro-D-Arg (PZ-peptide). The peptidase has been purified to homogeneity from chicken embryos. The enzyme has a pH optimum of 7.5 to 8.5, and isoelectric point of 5.0, and a molecular weight of 77,000. The kinetic parameters at pH 8 and 37 degrees are: Km = 2 X 10(-4) M and Vmax = 4.2 mumol/min/mg of protein. The enzyme is inhibited by p-hydroxymercuribenzoate (100%), N-ethylmaleimide (60%), and chelating agents (40 to 60%). Maximum activity is attained in the presence of reducing agents and Ca2+, Sr2+, or Mg2+. The peptidase has no detectable action on casein, serum albumin, collagen, collagen alpha chains, various collagen peptides (alpha1)(I)-CB2, alpha1(I)-CB3, alpha1(I)-CB4), (Gly-Pro-Pro)10, or (Gly-Pro-Pro)5. It does catalyze the hydrolysis of the Hyp--Gly bond in the 17-residue collagen peptide alpha1(II)-CB6-C2 and it partially digested a mixture of collagen peptides of molecular weight 350 to 2500. A role of this peptidase in collagen breakdown appears to be restricted to a late stage when degradation products would fall in the range of 5 to 30 residues.