Genome-wide identification and functional characterization of alpha-amylase genes in Litopenaeus vannamei

Alpha-amylase is a key enzyme involved in carbohydrate hydrolysis and food digestion in animals. However, its molecular characteristics and functions remain poorly understood in the economically important Pacific white shrimp, Litopenaeus vannamei. Through comparative genomic analysis, this study revealed that the α-amylase (Amy) gene family has undergone an expansion in arthropods, particularly crustaceans, while retaining highly conserved catalytic domains. Six Amy genes were identified in L. vannamei. Their expression patterns across tissues and developmental stages revealed predominant transcription in the hepatopancreas, with significant upregulation during periods of high energy demand, such as zoeal feeding and pre-molting. Among these genes, Lv-Amy (XP_027225605.1) exhibited the highest expression level. Quantitative real-time PCR (qPCR) and fluorescence in situ hybridization (FISH) further characterized the tissue distribution and cellular localization of Lv-Amy. Structurally, Lv-Amy displays a typical (β/α)₈ TIM barrel conformation and two conserved calcium-binding sites. The recombinant Lv-Amy protein was produced in an E. coli expression system and its enzymatic properties were characterized. Maximal activity of the recombinant Lv-Amy protein was observed at pH 7.5 and 25°C, while activity remained above 50% of the maximum within pH 7.0-8.0 and 20-45°C, indicating that Lv-Amy can function efficiently under environmental conditions characteristic of the tropical marine habitat of L. vannamei. In summary, this study provides new insights into the molecular characteristics and functions of α-amylase in L. vannamei, suggesting that Lv-Amy plays an important role in digestion and offering a reference of stage-specific nutritional formulation for this species.