Introduction of Oxidase and Oxygenase
Oxygenase is a general term for the oxidation reaction enzyme that catalyzes the binding of oxygen atoms of molecular oxygen to a substrate and belongs to the class of oxidoreductases. Oxidase can be divided into dioxygenase and monooxygenase which is also called mixed-function oxygenase or hydroxylase; the former is often accompanied by aromatic ring crack. Oxidase is the main enzyme of peroxidase in the body, and is accounted for about half of the total peroxidase enzyme in the body, including D - amino acid oxidase, uric acid oxidase, L- amino acid oxidase and L- α- hydroxy oxidase.
The Family Members of Oxygenase and Oxidase
Oxygenases are composed of several protein families that introduce one (monooxygenase) or two (dioxygenase) oxygen atoms into their substrate. Oxygen is usually supplied in the form of O2. The reduction equivalents required are usually obtained from NADH or NAD(P)H through electron transfer proteins (such as reductase). In general, oxidases catalyze a wide range of regioselective and stereoselective reactions. The monooxygenase-catalyzed hydroxylation and epoxidation reactions have special significance in chemical synthesis. Cytochrome P450 monooxygenase is a versatile super-family enzyme that catalyzes the oxidation of substrates such as alkanes to complex endogenous molecules such as steroids and fatty acids. P450s have been the subjects of many engineering studies to understand their function and performance, as well as to make better catalysts. Oxidase is a large family of enzymes, and enzymes in the family are also widely used in industry and aquaculture; for example, glucose oxidase is widely used in food quality and processing. Uric acid oxidase has received increasing attention as an effective therapeutic agent for controlling uric acid content, and polyphenol oxidase has also been widely used in the food industry.
The Application of Oxygenase in Different Disease
An adaptive change in human evolution is to resist external oxidative damage and maintain its stability. Superoxide dismutase, peroxidase, catalase and some non-enzymic substances, vitamin E and vitamin C, play an important role in resisting external oxidative damage, as well as the little-known heme oxygenas(OH). In addition, it is also important to maintain cell stability under stress conditions. Individuals with a deletion of ho gene are unable to grow normally and have increased sensitivity to oxidative damage until the final death. HO is the rate-limiting enzyme of heme oxidation. There are three isozymes in the body, HO-1, HO-2 and HO-3, which are encoded by different genes. They vary widely in molecular structure, expression regulation, and tissue distribution. At present, the research mainly focuses on the gene expression and regulation of HO-1 and its relationship with diseases. Of particular interest are HO and coronary artery disease (CAD), which are associated with oxygen free radical production, lipid peroxidation, atherosclerosis, and inflammation. Vascular atherosclerosis is mainly caused by the oxidation of low-density lipoproteins and phagocytosis by endothelial macrophages to form lipid-rich foam cells. Bilirubin prevents the oxidation of lipoproteins, especially low-density lipoproteins, and prevents the formation of atherosclerotic plaques. At the same time, bilirubin can scavenge oxygen free radicals and hydrogen peroxide associated with inflammation, protecting the myocardial cell membrane from oxidative damage. HO-1 can also influence the occurrence of CAD through other channels. For example, HO-1 decomposes hemoglobin (Heme), which reduces the oxidative damage of Heme to cardiomyocytes; the produced CO can increase cGMP in smooth muscle cells by activating ornithine cyclase, relax coronary artery smooth muscle, and inhibit platelet aggregation and vascular smooth muscle hyperplasia; HO-1 promotes increased ferritin synthesis and also eliminates cellular damage and chronic inflammation caused by intracellular iron. In conclusion, HO-1 and its metabolites can reduce the risk of CAD in different ways. In the past, myocardial remodeling was thought to be an adaptive change in ventricular wall stress caused by an increase in blood pressure or volumetric load, including an increase in myocardial cell volume and an increase in myocardial collagen synthesis. Although it is a cardiac function compensatory mechanism, the progressive development of pathological cardiac hypertrophy eventually leads to congestive heart failure. During cardiac remodeling, the myocardium continuously responds to extracellular stimuli such as mechanical stress, ischemia, oxygen free radicals, growth factors, vasoactive peptides, hormones, etc. so the amounts of myocardial cells increase, and collagen synthesis increases. Some researchers have found that HO-1 overexpression can alleviate cardiac hypertrophy caused by angiotensin-II (Ang-II) in Wister rats, but it cannot alleviate hypertension caused by Ang-II. This finding suggests that Ang-II-induced myocardial remodeling may not be directly secondary to Ang-II-induced hypertension, and that HO-1 may act directly on myocardial tissue rather than through myocardial regulation to reduce myocardial remodeling.