3.4.22.70 C184A catalytically inactive 717705 3.4.22.70 C184A mutant enzyme can not cleave the LPXTG motif 647382 3.4.22.70 C184A site-directed mutagenesis 731485 3.4.22.70 C184Hcy site-directed mutagenesis, generation of a sortase mutant with Cys184 replaced by homocysteine (Hcy). Mutant Hcy-sortase is a poor catalyst with less than 1% of wild-type activity. The sensitivity of the active site nucleophiles towards an alkylation reagent correlates with the pKa values of the mutated residues 731485 3.4.22.70 C184S 2700fold decrease in kcat/Km compared to wild-type value 678296 3.4.22.70 C184Sec site-directed mutagenesis, generation of a sortase mutant with Cys184 replaced by selenocysteine (Sec). Mutant Sec-sortase shows a moderate 2-3fold reduction in catalytic activity. The sensitivity of the active site nucleophiles towards an alkylation reagent correlates with the pKa values of the mutated residues. The pH-profile of mutant Sec-sortase is shifted to more acidic conditions when compared to the wild-type enzyme 731485 3.4.22.70 D170A Tm is 1.7°C higher than the Tm-value of wild-type enzyme. No change in kcat/Km compared to wild-type value 680902 3.4.22.70 D170A turnover-number for o-aminobenzoyl-LPETG-2,4-dinitrophenyl is nearly identical to wild-type value 665718 3.4.22.70 D185A 1.3 fold decrease in kcat/Km compared to wild-type value 678296 3.4.22.70 D186A 1.8fold decrease in kcat/Km compared to wild-type value 678296