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In microbial nitrogen metabolism, the occurrence of hydrazine as an intermediate is rare. [36] Hydrazine has been proposed as an enzyme-bound intermediate in the nitrogenase reaction. [37] Recently, using detailed molecular analyses and combining complementary methods, Kartal and coworkers published strong evidence supporting the latter mechanism.
Glutamine synthetase (GS) (EC 6.3.1.2) [3] is an enzyme that plays an essential role in the metabolism of nitrogen by catalyzing the condensation of glutamate and ammonia to form glutamine: Glutamate + ATP + NH 3 → Glutamine + ADP + phosphate Glutamine synthetase catalyzed reaction
The primary use is in the form of nitroglycerin, either pill or liquid spray forms, which, as a prodrug, is denitrated and releases the active metabolite nitric oxide (NO). As with all supplements of nitric oxide, the response is short-lived because, as a normally produced internal physiologic control mechanism, increased concentrations lead to ...
Nitric oxide synthases produce NO by catalysing a five-electron oxidation of a guanidino nitrogen of L-arginine (L-Arg). Oxidation of L-Arg to L-citrulline occurs via two successive monooxygenation reactions producing N ω-hydroxy-L-arginine (NOHLA) as an intermediate. 2 mol of O 2 and 1.5 mol of NADPH are consumed per mole of NO formed. [3]
HCC is the most common form of liver cancer and the third most common cause of cancer-related deaths worldwide. [12] The search for alternative treatment options remains a lucrative area of research as current available therapeutics (surgery, radiotherapy, chemotherapy) generally have severe side effects and/or low success rates with HCC. [ 12 ]
Anaplerotic reactions, a term coined by Hans Kornberg and originating from the Greek ἀνά= 'up' and πληρόω= 'to fill', are chemical reactions that form intermediates of a metabolic pathway. Examples of such are found in the citric acid cycle (TCA cycle). In normal function of this cycle for respiration, concentrations of TCA ...
Recent results, however, show that HAO does not produce nitrite as a direct product of catalysis. This enzyme instead produces nitric oxide and three electrons. Nitric oxide can then be oxidized by other enzymes (or oxygen) to nitrite. In this paradigm, the electron balance for overall metabolism needs to be reconsidered. [7]
The possibility of life-forms being based on "alternative" biochemistries is the topic of an ongoing scientific discussion, informed by what is known about extraterrestrial environments and about the chemical behaviour of various elements and compounds. It is of interest in synthetic biology and is also a common subject in science fiction.