$(i)$ તેઓ કેન્દ્રઅનુરાગી સમૂહોની અછત ધરાવે છે

$(ii)$ તેઓ અત્યંત વિશિષ્ટ હોય છે

$(iii)$ તેઓ પ્રક્રિયાની સક્રિયકરણ ઊર્જા ઘટાડી પ્રક્રિયાને  ઉદ્દીપિત કરે છે

$(iv)$ પેપ્સીન એ પ્રોટીયોલિટિક ઉત્સેચક છે

$\begin{align}
  & \begin{matrix}
   O\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,  \\
   ||\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,  \\
   H-O-C-C{{H}_{2}}-C{{H}_{2}}-CH-C{{O}_{2}}H  \\
   \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,|  \\
   \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\underset{\oplus }{\mathop{N}}\,{{H}_{3}}  \\
\end{matrix}\,\,\,\,\,(p{{K}_{a}}=2) \\ 
 & (p{{K}_{a}}=4)\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,(p{{K}_{a}}=9) \\ 
\end{align}$