L-histidine is an alkalescency amino acid with an imidazole group.It's a semi-essential amino acid in human and animals.L-histidine is one of the components of protein construction,it participates in the protein synthesizing and many kinds of physiological and biochemiscal process by different forms.L-histidine has various functions enable it to be applied in food,health product,feed,chemical industry,medicine and other fields.The paper briefly introduces synthesis pathways,regulation mechanism,breeding pla...