[Applications and synthesis of D-amino acids]

D-amino acids, chiral molecules with unique physiological activities, present widely distribution in microorganisms, plants, and animals. With the deepening of research, D-amino acids are playing increasingly important roles in food, pharmaceuticals, agrochemicals, cosmetics and other fields. However, the natural abundance of D-amino acids is low. Chemical synthesis methods suffer from low stereoselectivity, serious environmental pollution, and high production costs, which limit their industrial application. Enzymatic synthesis has emerged as a cutting-edge research focus for D-amino acid production due to its high stereoselectivity, mild reaction conditions, and environmental friendliness. Currently, enzymes commonly used for D-amino acid synthesis include D-amino acid dehydrogenase, L-amino acid oxidase, D-amino acid aminotransferase, D-aminoacylase, D-hydantoinase, and D-carbamoylase. These enzymes employ various mechanisms to convert substrates or resolve racemic mixtures, or establish multi-enzyme cascade reactions to synthesize diverse D-amino acids and their derivatives. This review summarizes the latest advances in the enzymatic synthesis of D-amino acids, explores the catalytic mechanisms and optimization strategies of various enzymes, and examines the performance of these enzymes in practical applications, providing theoretical support and technical guidance for the efficient and green synthesis of D-amino acids.