Kinetic analysis of dye-linked dehydrogenases and related enzymes where the electron acceptor binds twice during the catalytic sequence

Managing rheumatic diseases during COVID-19

Rheumatology practice, during Coronavirus Disease 2019 (COVID-19) pandemic, has faced multifaceted challenges. Rheumatologists routinely prescribe immunosuppressant medications to their patients with multisystem autoimmune rheumatic diseases who are concerned about the increased risk of acquiring COVID-19 infection and are anxious to know if they should continue or hold these medications. Rheumatologists are often inundated by calls from their patients and physician colleagues caring for COVID-19 patients in hospitals, about how to manage the immunosuppression. Physicians face the challenging task of keeping up with the most up-to-date information on COVID-19. There are uncertainties about the mode of spread, clinical features, management options as well as long-term complications of COVID-19. Data are rapidly evolving and different studies on treatment options are showing contradictory results. It is known that viral illnesses can trigger a flare-up of underlying rheumatic disease that was previously in remission. To further complicate the scenario, some of the immunosuppressants have shown to have antiviral properties. This has created dilemma in the light of current COVID-19 crisis, as whether to continue or stop the immunosuppressive agents which could be essential to prevent complications of the rheumatic diseases including organ failure but also there is concern about acquiring COVID-19 or developing serious infection. Until we get an effective vaccine, immunosuppressant management for rheumatic diseases as well as other autoimmune diseases and transplants will pose difficult questions. This article is an attempt to review and understand COVID-19 and its impact on the immune system with special emphasis on managing medications used for autoimmune rheumatic diseases. We have provided general guidance about decision making, in regards to the immunosuppressive agents used in rheumatology practice with an understanding that this may change in near future.

Potential new treatment strategies for COVID-19: is there a role for bromhexine as add-on therapy?

Of huge importance now is to provide a fast, cost-effective, safe, and immediately available pharmaceutical solution to curb the rapid global spread of SARS-CoV-2. Recent publications on SARS-CoV-2 have brought attention to the possible benefit of chloroquine in the treatment of patients infected by SARS-CoV-2. Whether chloroquine can treat SARS-CoV-2 alone and also work as a prophylactic is doubtful. An effective prophylactic medication to prevent viral entry has to contain, at least, either a protease inhibitor or a competitive virus ACE2-binding inhibitor. Using bromhexine at a dosage that selectively inhibits TMPRSS2 and, in so doing, inhibits TMPRSS2-specific viral entry is likely to be effective against SARS-CoV-2. We propose the use of bromhexine as a prophylactic and treatment. We encourage the scientific community to assess bromhexine clinically as a prophylactic and curative treatment. If proven to be effective, this would allow a rapid, accessible, and cost-effective application worldwide.

Steady-state study of the mechanism of dopa-oxidase activity of tyrosinase

The mechanism of the dopa-oxidase activity of frog epidermis tyrosinase has been studied. Initial reaction rates have been measured as function of substrate concentrations, L-dopa and oxygen, in the presence and absence of an inhibitor, product of the reaction. Initial reaction rates versus substrate concentrations, without inhibitor, show a linear dependence in the double-reciprocal space, that discarded Ordered and Random mechanisms. Initial reaction rates versus substrate concentrations, in the presence of an inhibitor product of the reaction, show a non-linear dependence in the double-reciprocal space. This point, joined to the former one, indicates a Ping-Pong mechanism, different of the Hexa-Uni type. The reaction is discussed for first time taking into account a trisubstrate mechanism. The experimental results lead to an (Uni Uni Bi Uni) Ping-Pong mechanism. On the other hand, they can explain the differences between known data of tyrosinases from several sources. Michaelis constant have been calculated for both substrates. The values are 0.16 and 7.14 mM for oxygen and L-dopa respectively.