4-aminobutanoate + L-histidine + ATP = L-homocarnosine + ADP + phosphate + H(+)
4-aminobutanoate + l-histidine + atp = l-homocarnosine + adp + phosphate + h(+)
4-aminobutanoate + L-histidine + ATP = L-homocarnosine + ADP + phosphate + H(+)
4-aminobutanoate + l-histidine + atp = l-homocarnosine + adp + phosphate + h(+)