The decreased activity by 50 fold and the kinetic isotope effects show that CH1 bond cleavage is more rate-limited in the Y429F mutant, consistent with the proposed proton shuttling by Tyr429.

• 其中Y429F突变株酵素活性下降约50倍，且从其动力学同位素效应结果显示，Y429的突变使CH1键结断裂的速率更受到限制，乃符合Y429作为活性中心碱基之推测。