Sphingomyelin synthase (SMS) sits at the crossroads of sphingomyelin (SM), ceramide, diacylglycerol (DAG) metabolism. It utilizes ceramide and phosphatidylcholine as substrates to produce SM and DAG, thereby regulating lipid messengers which play a role in cell survival and apoptosis. There are two isoforms of the enzyme, SMS1 and SMS2. Both SMS1 and SMS2 contain two histidines and one aspartic acid which are evolutionary conserved within the lipid phosphate phosphatase superfamily. In this study, we systematically mutated these amino acids using site-directed mutagenesis and found that each point mutation abolished SMS activity without altering cellular distribution. We also explored the domains which are responsible for cellular distribution of both enzymes. Given their role as a potential regulator of diseases, these findings, coupled with homology modeling of SMS1 and SMS2, will be useful for drug development targeting SMS.

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Purpose To ensure the mental health of the otolaryngology healthcare workers in the fight against coronavirus disease 2019 (COVID-19), it is important to know their mental status and to identify possible risk factors. In this study, we investigated the risk factors for the anxiety in the otolaryngology healthcare workers in Hubei province under the COVID-19 epidemic. Methods The otolaryngology healthcare workers in Hubei Province were surveyed using an online questionnaire in which anxiety was measured against the Zung Self-rating Anxiety Scale. Univariate and multivariate logistic regression analyses were used to evaluate the risk factors of anxiety. Results A total of 449 otolaryngology healthcare workers participated in the study. Of all the participants, 131 (29.18%) had anxiety symptoms. Compared with doctors, nurses were at a higher risk for anxiety (OR = 2.162, 95% CI 1.311-3.566). Participants who often suspected self-infection (OR = 4.239, 95% CI 1.647-10.909) or family member infection by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (OR = 4.485, 95% CI 1.511-13.313) were more likely to develop anxiety than those who never. The subjects who had colleagues diagnosed with COVID-19 were more vulnerable to anxiety (OR = 2.014, 95% CI 1.205-3.366). Respondents working in infectious isolation wards had a 3.522-fold increased risk of anxiety compared to those on leave (OR = 3.522, 95% CI 1.634-7.593). Conclusion Some otolaryngology healthcare workers in Hubei province experienced anxiety during the epidemic, but most of them did not receive treatment. The healthcare providers themselves should be informed about and aware of their own mental health, and should be given support as appropriate. Trial registration number and date of registration Chinese Clinical Trial Registry: ChiCTR2000030768, 2020/3/14.

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