label: an N-terminal L-alpha-aminoacyl-[protein] + acetyl-CoA = N-terminal N(alpha)-acetyl-L-alpha-aminoacyl-[protein] + CoA + H(+)
label_lc: an n-terminal l-alpha-aminoacyl-[protein] + acetyl-coa = n-terminal n(alpha)-acetyl-l-alpha-aminoacyl-[protein] + coa + h(+)