Which of the following statements about protein kinase-based signaling is false?

Which of the following statements about protein kinase-based signaling is false?

Which of the following statements about protein kinase-based signaling is false?





  1. Serine and threonine kinases are typically activated by second messengers.
  2. Tyrosine kinases are typically activated by extracellular signals.
  3. Each protein kinase has just one specific target protein that it phosphorylates.
  4. The effects of protein kinases can be balanced by protein phosphatases.
  5. Thousands of protein kinases are expressed in the brain.

Answer: 3