Description: This structure of the thermostable acetyl esterase TM0077 from Thermotoga maritima reveals a classic α/β-hydrolase fold assembled into a doughnut-shaped hexamer. The structure confirms the catalytic serine mechanism and reclassifies the enzyme’s activity from acetyl xylan esterase to a short-chain acetyl esterase, with relevance to industrial biocatalysis at extreme temperatures.