Table 3.

Summary of congenital ChAT mutations^a

Mutation	Damaginga SIFT Score	ChAT activity affected	Location on Sec. structure	Mutation probable structural effect
p.Val136Met	yes 0	↓ $K_m^{AcCoA}$ Lowest enzyme expression	Coil 1 before α-helix 1 binding domain	Possible energetic interaction with AcCoA
p.Arg186Trp	yes 0	↓↓ kcat, ↓$K_m^{AcCoA}$	α-helix 3 binding domain	Destabilize enzyme folding
p.Val194Leu	tolerated 1	↑↑kcat, ↑↑$K_m^{AcCoA}$ ↑$K_m^{choline}$	Coil 3 before α- helix 4 binding domain	Alter AcCoA binding site
p.Arg207His	yes 0	↓↓kcat, ↓↓$K_m^{AcCoA}$ Low ChAT expression	Coil 5 between α-helix 4 and β-sheet 1 binding domain	Modify active site, close to His424
p.Pro211Ala	tolerated 0.39	↑ kcat, ↑↑$K_m^{AcCoA}$	Coil 5 before β-sheet 1 catalytic domain	Change active site and choline-binding site
p.Arg566Cys	tolerated 1	↓ kcat, ↑$K_m^{AcCoA}$ $K_m^{choline}$	β-sheet 12 binding domain	Disrupt H-bond with His424 at active site
p.Ser694Cys	Yes 0	↓ kcat, ↑↑$K_m^{choline}$	β-sheet 16 binding domain	Disrupt H-bond with Tyr670 involved in choline binding

↑, increase in the K_m value; ↑↑, large increase in the K_m value; ↓, decrease in the K_m value; ↓↓, large decrease in the Km value.

^aSIFT score predicts whether an amino acid substitution affects protein function based on sequence homology and the physical properties of amino acids.