4-aminobutanoate + L-lysine => N(2)-(4-aminobutanoyl)-L-lysine + H2O
4-aminobutanoate + l-lysine => n(2)-(4-aminobutanoyl)-l-lysine + h2o
4-aminobutanoate + L-lysine => N(2)-(4-aminobutanoyl)-L-lysine + H2O
4-aminobutanoate + l-lysine => n(2)-(4-aminobutanoyl)-l-lysine + h2o