Activation of protein kinase, such as JNK and Akt, plays an important role in apoptosis and other physiological and pathological processes. BioVision provides a novel nonradioactive system for convenient measurement of JNK and Akt activities. The JNK Activity Screening Kit is used to screen JNK activity relatively quickly for large numbers of samples. The assay utilizes a N-terminal c-Jun fusion protein bead to selectively “pull down” JNK from cell lysate. c-Jun phosphorylation is then measured using a phospho-c-Jun specific antibody. The KinaseSTARTM JNK or Akt Activity Assay Kit utilizes a JNK- (or Akt-) specific antibody to immunoprecipitate JNK (or Akt) from cell lysate. JNK- (or Akt-) specific activity is then analyzed by Western blot analysis of the phosphorylation levels of c-Jun (or GSK-3a) using a phospho-c-Jun (or phospho-GSK-3a) specific antibody. The kit specifically detects JNK (or Akt) activity, other kinase activities would not be detected.