Tyrosine metabolic enzymes from insects and mammals: A comparative perspective

Abstract

Differences in the metabolism of tyrosine between insects and mammals present an interesting example of molecular evolution. Both insects and mammals possess fine-tuned systems of enzymes to meet their specific demands for tyrosine metabolites; however, more homologous enzymes involved in tyrosine metabolism have emerged in many insect species. Without knowledge of modern genomics, one might suppose that mammals, which are generally more complex than insects and require tyrosine as a precursor for important catecholamine neurotransmitters and for melanin, should possess more enzymes to control tyrosine metabolism. Therefore, the question of why insects actually possess more tyrosine metabolic enzymes is quite interesting. It has long been known that insects rely heavily on tyrosine metabolism for cuticle hardening and for innate immune responses, and these evolutionary constraints are likely the key answers to this question. In terms of melanogenesis, mammals also possess a high level of regulation; yet mammalian systems possess more mechanisms for detoxification whereas insects accelerate pathways like melanogenesis and therefore must bear increased oxidative pressure. Our research group has had the opportunity to characterize the structure and function of many key proteins involved in tyrosine metabolism from both insects and mammals. In this mini review we will give a brief overview of our research on tyrosine metabolic enzymes in the scope of an evolutionary perspective of mammals in comparison to insects.

Composition and emission dynamics of migratory locust volatiles in response to changes in developmental stages and population density

“…This characteristic may suggest that the volatile compound produced by two locust species involves the same biosynthetic pathway in vivo and plays similar roles in chemical communication between conspecific individuals. Although phenylalanine has been proven to be a precursor for the biosynthesis of PAN in the desert locust , this biosynthetic pathway is conserved from microbe to plants and to animals (Asano & Kato, 1998;Irmisch et al, 2014;Vavricka et al, 2014). This compound has been reported as a mature male-specific component in the desert locust, serving as an aggregation pheromone of adults, but not nymphs (Torto et al, 1994;Hassanali et al, 2005;Rono et al, 2008), as a courtship inhibition pheromone in malemale competition and homosexual attempt (Seidelmann et al, 2005), or as a maturation-accelerating pheromone (Mahamat et al, 2011).…”

3,4-Dihydroxyphenylacetaldehyde synthase and cuticle formation in insects

“…Dopamine, derived from tyrosine, is the key component for the synthesis of both NADA and NBAD. Tyrosine is first hydroxylated to 3,4-dihydroxyphenylalanine (dopa) by a tyrosine hydroxylase (TH) and the latter is then decarboxylated by dopa decarboxylase to dopamine (Andersen, 2010;Han et al, 2010;Vavricka et al, 2014). Dopamine can be either acetylated by arylalkylamine N-acetyltransferase (aaNAT) to produce NADA (Mehere et al, 2011;Han et al, 2012) or conjugated with b-alanine to synthesize NBAD by N-b-alanyl dopamine synthase (Ebony protein) in the presence of ATP (Hovemann et al, 1998).…”

“…As described above, L-dopa is the key precursor for the cuticle tanning and melanization pathway in the formation of rigid cuticle, but L-dopa is also the immediate precursor for the production of DOPAL predicted to crosslink cuticular proteins in flexible cuticle (Vavricka et al, 2010(Vavricka et al, , 2014. DOPAL, produced by DOPAL synthase, is highly reactive, and can directly participate in protein crosslinking through its interaction with free amino groups on cuticular proteins (such as the free amine from lysine residues).…”

Macroevolutionary patterns in overexpression of tyrosine: An anti‐herbivore defence in a speciose tropical tree genus, Inga (Fabaceae)

“…Previously, we found overexpression of the essential amino acid L‐tyrosine in one species, Inga umbellifera (Lokvam et al, ). Tyrosine is a key nutrient for herbivores, involved in protein biosynthesis, cuticle hardening and innate immune responses (Vavricka et al, ). Tyrosine is generally present at very low concentrations in mature leaves, including mature leaves of I. umbellifera (0.05% DW, Lokvam et al, ).…”