The enhancing of a cysteine proteinase activity at acidic pH by protein engineering, the role of glutamic 50 in the enzyme mechanism of caricain.

@article{Ikeuchi1998TheEO,
  title={The enhancing of a cysteine proteinase activity at acidic pH by protein engineering, the role of glutamic 50 in the enzyme mechanism of caricain.},
  author={Yukako Ikeuchi and Nikolaos A Katerelos and Peter W. Goodenough},
  journal={FEBS letters},
  year={1998},
  volume={437 1-2},
  pages={91-6}
}
Carica papaya produces four cysteine proteinases. Calculations show that the Cys25, His159 essential ion pair is fully ionised at pH 2.99, where activity cannot be detected, but apparently an additional ionisation with a pKa of 4 is essential for activity (an electrostatic switch). Caricain (EC 3.4.22.30) wt and D158E genetic backgrounds were used to study the contribution of E50A to activity. E50 or E135 are candidates for the switch, E50A would be expected to reduce activity. However… CONTINUE READING

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