Research progress on tyrosine hydroxylase and dopa decarboxylase in insects

Tyrosine hydroxylase (TH) is the initial rate-limiting synthase involved in the synthesis of dopamine (DA), and dopa decarboxylase (DDC) is involved in the final step of DA synthesis, which converts L-3,4-dihydroxyphenylalanine (L-DOPA) to DA, and both enzymes play important roles in DA synthesis. DA is an important neurotransmitter in insects, exerting key functions in the regulation of various physiological and behavioral processes of insects, such as development, feeding, immunity, courtship and mating. In this review, we mainly introduce the relevant research progress on the gene expressions of TH and DDC in insects, the mechanisms involved in DA synthesis, and the physiological functions of these two enzymes, and we also presented the prospects for the future research and application prospects.