Catalase is a common enzyme found in nearly all living organisms exposed to oxygen (such as vegetables, fruit or animals). It catalyzes the decomposition of hydrogen peroxide to water and oxygen. It is a very important enzyme in protecting the cell from oxidative damage by reactive oxygen species (ROS). Likewise, catalase has one of the highest turnover numbers of all enzymes; one catalase molecule can convert millions of molecules of hydrogen peroxide to water and oxygen each second. Catalase is a tetramer of four polypeptide chains, each over 500 amino acids long. It contains four porphyrin heme (iron) groups that allow the enzyme to react with the hydrogen peroxide. The optimum pH for human catalase is approximately 7, and has a fairly broad maximum (the rate of reaction does not change appreciably at pHs between 6.8 and 7.5). The pH optimum for other catalases varies between 4 and 11 depending on the species. The optimum temperature also varies by species. This video is targeted to blind users. Attribution: Article text available under CC-BY-SA Creative Commons image source in video
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The N Engl J Med image of the week shows a young woman with a generalized morbilliform eruption over her entire body; the chest is most prominent. She wears eye protection because of photophobia. You are offered polymorphous light eruption, Dengue fever, measles, Stevens-Johnson syndrome and acute cutaneous lupus erythematosis. Herpes Zoster is a reactivation of varicella virus that plagues older adults and immunosuppressed persons, although zoster can appear at almost any age. A vaccine is available. We inspect a better vaccine based on expression of the virus glycoprotein E recombinantly. The vaccine in two doses of HZ/su administered 2 months apart had a vaccine efficacy of 97.2%, as compared with placebo, in reducing the risk of herpes zoster in adults 50 years of age or older. Meiosis is a specialized type of cell division, which reduces the chromosome number by half. The process is crucial to species survival and is thus carefully genetically regulated. The genetic basis of nonobstructive azoospermia is unknown in the majority of infertile men; meiosis regulators could play a role. Investigators performed array comparative genomic hybridization (aCGH) in blood samples obtained from patients with azoospermia and mutation screening by means of direct Sanger sequencing of the testis-expressed 11 (TEX11) gene open reading frame in patients with azoospermia and controls. TEX11 mutations occurred in infertile men with meiotic arrest. The finding is important for the diagnosis of azoospermia and meiotic arrest. It is also important for preconception testing in men who are partners of women undergoing in vitro fertilization, intracytoplasmic sperm injection, or both. Financial incentives promote many health behaviors, but effective ways to deliver health incentives remain uncertain. Psychologists randomly assigned CVS Caremark employees and their relatives and friends to one of four incentive programs or to usual care for smoking cessation. Would you believe that paying people to stop smoking is successful? Anything can be had for money! The natural history of tuberculosis begins with the inhalation of Mycobacterium tuberculosis organisms; a period of bacterial replication and dissemination ensues, followed by immunologic containment of viable bacilli. This state-of-affairs is called latent tuberculosis and almost everyone in my generation has it. The chances of developing clinical tuberculosis at a later timepoint is 5-15%, N Engl J Med reviews this important topic. The N Engl J Med case is a middle-aged nonsmoking woman with non-small-cell lung cancer. She develops intractable pain. Her terminal treatment is termed “palliative sedation”. The distinction between this approach and assisted suicide is discussed. Inhibition of cholesteryl ester transfer protein has been shown to reduce LDL-C concentrations in addition to regular statin treatment in patients with hypercholesterolaemia or at high risk of cardiovascular disease. Inhibitors thus far have not prolonged life of persons at risk from cardiovascular disease. Nonetheless, in the Lancet we review a paper on a CETP inhibitor in patients with familial hypercholesterolemia. In the fetus, the ductus venosus shunts a portion of the left umbilical vein blood flow directly to the inferior vena cava. Thus, the ductus-venosus shunt allows oxygenated blood from the placenta to bypass the liver. Increased impedance to flow in the fetal ductus venosus at 11-13 weeks’-gestation is associated with fetal aneuploidies, cardiac defects and other adverse pregnancy outcomes. No consensus exists for the best way to monitor and when to trigger delivery in mothers of babies with fetal growth restriction. Lancet investigators aimed to assess whether or not changes in the fetal ductus venosus Doppler waveform could be used as indications for delivery instead of cardiotocography short-term variation (STV). Unfortunately, the results do not inspire confidence. Mortality in people in Africa with HIV infection starting antiretroviral therapy (ART) is high, particularly in those with advanced disease, commonly complicated by cryptococcal meningitis, a treatable fungal meningeal disease. Therefore, investigators assessed the effect of a short period of community support to supplement clinic-based services combined with serum cryptococcal antigen screening. Just four short home visits by lay workers to provide adherence support combined with screening for cryptococcal meningitis led to a significant reduction in mortality in patients infected with HIV starting ART with advanced disease. The brachial plexus is a network of nerves, running from the spine, formed by the anterior rami of the lower four cervical nerves and first thoracic nerve (C5–C8, T1). Brachial plexus injuries can permanently impair hand function, yet present surgical reconstruction provides only poor results.
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