16 Questions
What metal ions are crucial for creatine kinase activity?
Magnesium ions (Mg2+) are crucial for creatine kinase activity and form complexes with ATP and ADP, serving as obligate activating ions.
What is the role of creatine kinase in cellular energy metabolism?
Creatine kinase plays a crucial role in cellular energy metabolism, particularly in muscle cells, by catalyzing the reversible phosphorylation of creatine by ATP.
What is the optimal pH value for the forward reaction of creatine kinase?
The forward reaction of creatine kinase, which generates ATP from creatine phosphate, is favored at a pH of 9.0.
What metal ions inhibit creatine kinase activity?
Metal ions like manganese (Mn2+), calcium (Ca2+), zinc (Zn2+), and copper (Cu2+) inhibit creatine kinase activity.
What is the molecular weight of creatine kinase?
Creatine kinase is a dimeric enzyme with a molecular weight of 82 kDa.
What is the role of creatine kinase during muscle contraction?
During muscle contraction, creatine kinase catalyzes the rephosphorylation of ADP back to ATP using creatine phosphate as a reservoir of high-energy phosphate, essential for sustaining muscle function during periods of high energy demand.
What compounds negatively affect CK activity?
Excess ADP, citrate, fluoride, nitrate, acetate, iodide, bromide, malonate, L-thyroxine, urate, cystine, chloride ions, and sulfate ions
Why is maintaining low concentrations of chloride and sulfate ions essential in enzyme assay systems based on the reverse reaction?
To prevent inhibition of CK activity
Which sulfhydryl compounds can help restore some of the lost activity of creatine kinase?
N-acetylcysteine, dithiothreitol (Cleland reagent), and glutathione
What is the advantage of using N-acetylcysteine in current assays?
High solubility and typically used at a final concentration of 20 mmol/L
Which tissues contain the highest levels of CK activity?
Striated muscle and heart tissue
Which tissues exhibit significantly lower levels of CK activity compared to striated muscle and heart tissue?
Brain, smooth muscles of the gastrointestinal tract, and urinary bladder
Which tissues are essentially devoid of CK activity?
Liver and erythrocytes
What are the molecular weights of the subunits composing creatine kinase?
Around 40 kDa
How many distinct pairs of subunits can combine to form various isoenzymes of creatine kinase?
Three
Based on electrophoretic mobility, how have the isoenzymes of creatine kinase been named?
Using their electrophoretic mobility as a basis
Learn about the role of creatine kinase and aldolase enzymes in muscle cells and cellular energy metabolism. Understand their functions and importance during muscle contraction and in relation to ATP and ADP conversion.
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