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- Branneby, Cecilia, et al.
(författare)
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Carbon-Carbon Bonds by Hydrolytic Enzymes
- 2003
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 125:4, s. 874-875
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Tidskriftsartikel (refereegranskat)abstract
- Enzymes are efficient catalysts in synthetic chemistry, and their catalytic activity with unnatural substrates in organic reaction media is an area attracting much attention. Protein engineering has opened the possibility to change the reaction specificity of enzymes and allow for new reactions to take place in their active sites. We have used this strategy on the well-studied active-site scaffold offered by the serine hydrolase Candida antarctica lipase B (CALB, EC 3.1.1.3) to achieve catalytic activity for aldol reactions. The catalytic reaction was studied in detail by means of quantum chemical calculations in model systems. The predictions from the quantum chemical calculations were then challenged by experiments. Consequently, Ser105 in CALB was targeted by site-directed mutagenesis to create enzyme variants lacking the nucleophilic feature of the active site. The experiments clearly showed an increased reaction rate when the aldol reaction was catalyzed by the mutant enzymes as compared to the wild-type lipase. We expect that the new catalytic activity, harbored in the stable protein scaffold of the lipase, will allow aldol additions of substrates, which cannot be reached by traditional aldolases
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- Riman, Tomas, et al.
(författare)
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Hormone replacement therapy and the risk of invasive epithelial ovarian cancer in Swedish women
- 2002
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Ingår i: Journal of the National Cancer Institute. - : Oxford University Press (OUP). - 0027-8874 .- 1460-2105. ; 94:7, s. 497-504
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Estrogen replacement therapy (ERT), which is mainly used to relieve climacteric symptoms, increases a woman's risk for uterine endometrial cancer and epithelial ovarian cancer (EOC). Estrogens are often combined with progestins in hormone replacement therapy (HRT) to reduce the risk of uterine endometrial cancer. Data on the association between HRT including progestins and EOC risk are limited. This nationwide case-control study examined EOC risk in relation to HRT regimens with sequentially added progestins (HRTsp) and continuously added progestins (HRTcp). METHODS: Between 1993 and 1995, we enrolled 655 histologically verified incident case patients with EOC and 3899 randomly selected population controls, all 50-74 years of age. Data on HRT use were collected through mailed questionnaires. Multivariate-adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were estimated by the use of unconditional logistic regression. RESULTS: Risks of EOC were elevated among ever users as compared with never users of both ERT (OR = 1.43, 95% CI = 1.02 to 2.00) and HRTsp (OR = 1.54, 95% CI = 1.15 to 2.05); risks were elevated for serous, mucinous, and endometrioid subtypes. For all EOC types combined, the greatest risk increases were seen with hormone use exceeding 10 years. Ever use of HRTcp was not associated with increased EOC risk relative to HRTcp never use (OR = 1.02, 95% CI = 0.73 to 1.43). The risk of EOC was elevated among HRTsp ever users as compared with HRTcp ever users (OR = 1.78, 95% CI = 1.05 to 3.01). ORs for EOC after ever use of low-potency estrogens were 1.18 (95% CI = 0.89 to 1.55) for oral and 1.33 (95% CI = 1.03 to 1.72) for vaginal applications, but no relationship was seen between EOC risk and duration of use. CONCLUSION: Ever users of ERT and HRTsp but not HRTcp may be at increased risk of EOC.
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