BackgroundMicrobial enzymes produced in the gastrointestinal tract are primarily responsible for the release and biochemical transformation of absorbable bioactive monophenols. In the present work we described the crystal structure of LJ0536, a serine cinnamoyl esterase produced by the probiotic bacterium Lactobacillus johnsonii N6.2.Methodology/Principal FindingsWe crystallized LJ0536 in the apo form and in three substrate-bound complexes. The structure showed a canonical α/β fold characteristic of esterases, and the enzyme is dimeric. Two classical serine esterase motifs (GlyXSerXGly) can be recognized from the amino acid sequence, and the structure revealed that the catalytic triad of the enzyme is formed by Ser106, His225, and Asp197, while the other motif is non-functional. In all substrate-bound complexes, the aromatic acyl group of the ester compound was bound in the deepest part of the catalytic pocket. The binding pocket also contained an unoccupied area that could accommodate larger ligands. The structure revealed a prominent inserted α/β subdomain of 54 amino acids, from which multiple contacts to the aromatic acyl groups of the substrates are made. Inserts of this size are seen in other esterases, but the secondary structure topology of this subdomain of LJ0536 is unique to this enzyme and its closest homolog (Est1E) in the Protein Databank.ConclusionsThe binding mechanism characterized (involving the inserted α/β subdomain) clearly differentiates LJ0536 from enzymes with similar activity of a fungal origin. The structural features herein described together with the activity profile of LJ0536 suggest that this enzyme should be clustered in a new group of bacterial cinnamoyl esterases.

Introduction Western militaries have consumption rates of alcohol and tobacco which are higher than the associated civilian populations, and are concerned about the negative effects on health, wellbeing, and military performance that such high rates may have. Materials and Methods A survey questionnaire which collected nonidentifiable data was distributed to all accessible members of an Australian Army Combat Brigade over the annual induction training and prefield exercise period between January and March 2019. The survey was composed of personal and demographic questions, followed by questions concerning the personal consumption habits of alcohol and tobacco. 1,606 complete and valid surveys were returned, representing 55.3% of the Brigade’s posted strength. Ethical clearance for this project was provided by the Australian Defence Force Joint Health Command Low Risk Ethics Panel (18-012). Results Almost one quarter of the Combat Brigade exceeded the Australian daily risk guideline for alcohol consumption, and over three quarters exceeded the occasion risk guideline; with 6.1% of soldiers drinking alcohol daily. 24.3% identified as tobacco smokers, with 15.9% smoking daily. Smoking rates and volumes were higher when deployed on field training exercises and on international training and operational deployments; as was the consumption of roll-your-own cigarettes. Overall, the main determinants of the negative consumption behaviors were gender (male) and age (under 25). Conclusions This study confirmed that the members of an Australian Army Combat Brigade have higher negative health consumption behaviors concerning alcohol and tobacco than the general civilian population. The results also identified a cohort of Senior Non-Commissioned Officers and Warrant Officers (E5–E9) between the ages of 35 and 44 who had high negative consumption behaviors which could result in poor health outcomes. This could be a suitable cohort for a targeted campaign to reduce tobacco and alcohol consumption and to assist to make healthy life changes.

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