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The acrosome is an organelle that develops over the anterior (front) half of the head in the spermatozoa of humans, and many other animals. It is a cap-like structure derived from the Golgi apparatus. In placental mammals the acrosome contains degradative enzymes. These enzymes break down the outer membrane of the ovum, called the zona pellucida, allowing the haploid nucleus in the sperm cell to join with the haploid nucleus in the ovum. This shedding of the acrosome, or acrosome reaction, can be stimulated in vitro by substances a sperm cell may encounter naturally such as progesterone or follicular fluid, as well as the more commonly used calcium ionophore A23187. This can be done to serve as a positive control when assessing the acrosome reaction of a sperm sample by flow cytometry or fluorescence microscopy. This is usually done after staining with a fluoresceinated lectin such as FITC-PNA, FITC-PSA, FITC-ConA, or fluoresceinated antibody such as FITC-CD46.
In biochemistry, Michaelis–Menten kinetics, named after Leonor Michaelis and Maud Menten, is the simplest case of enzyme kinetics, applied to enzyme-catalysed reactions of one substrate and one product. It takes the form of an equation describing the rate reaction rate to , the concentration of the substrate A. Its formula is given by the Michaelis–Menten equation:
Glycosaminoglycans (GAGs) or mucopolysaccharides are long, linear polysaccharides consisting of repeating disaccharide units. The repeating two-sugar unit consists of a uronic sugar and an amino sugar, except in the case of the sulfated glycosaminoglycan keratan, where, in place of the uronic sugar there is a galactose unit. GAGs are found in vertebrates, invertebrates and bacteria. Because GAGs are highly polar molecules and attract water; the body uses them as lubricants or shock absorbers.
Hyaluronidases are a family of enzymes that catalyse the degradation of hyaluronic acid. Karl Meyer classified these enzymes in 1971, into three distinct groups, a scheme based on the enzyme reaction products. The three main types of hyaluronidases are two classes of eukaryotic endoglycosidase hydrolases and a prokaryotic lyase-type of glycosidase.
Hyaluronic acid, also called hyaluronan, is an anionic, nonsulfated glycosaminoglycan distributed widely throughout connective, epithelial, and neural tissues. It is unique among glycosaminoglycans as it is non-sulfated, forms in the plasma membrane instead of the Golgi apparatus, and can be very large: human synovial HA averages about 7 million Da per molecule, or about 20,000 disaccharide monomers, while other sources mention 3–4 million Da.
Enzyme kinetics is the study of the rates of enzyme-catalysed chemical reactions. In enzyme kinetics, the reaction rate is measured and the effects of varying the conditions of the reaction are investigated. Studying an enzyme's kinetics in this way can reveal the catalytic mechanism of this enzyme, its role in metabolism, how its activity is controlled, and how a drug or a modifier might affect the rate.
The enzyme chondroitin B lyase catalyzes the following process:
The enzyme hyaluronate lyase catalyzes the chemical reaction
Cutis verticis gyrata is a medical condition usually associated with thickening of the scalp. The condition is identified by excessive thickening of the soft tissues of the scalp and characterized by ridges and furrows, which give the scalp a cerebriform appearance. Clinically, the ridges are hard and cannot be flattened on applying pressure. Patients show visible folds, ridges or creases on the surface of the top of the scalp. The number of folds can vary from two to roughly ten and they are typically soft and spongy. The condition typically affects the central and rear regions of the scalp, but sometimes can involve the entire scalp.
WW domain-containing oxidoreductase is an enzyme that in humans is encoded by the WWOX gene.
Hyaluronidase-2 is a multifunctional protein, previously thought to only possess acid-active hyaluronan-degrading enzymatic function. In humans it is encoded by the HYAL2 gene.
Hyaluronidase-1 is an enzyme that in humans is encoded by the HYAL1 gene.
Hyaluronan synthase 1 is an enzyme that in humans is encoded by the HAS1 gene.
Hyaluronidase PH-20 is an enzyme that in humans is encoded by the SPAM1 gene.
Hyaluronidase-3 is an enzyme that in humans is encoded by the HYAL3 gene.
Sodium hyaluronate is the sodium salt of hyaluronic acid, a glycosaminoglycan found in various connective tissue of humans.
In molecular biology, glycoside hydrolase family 56 is a family of glycoside hydrolases.
Attempts in the last decade to develop surgical treatments based on MRI and CAT scans now receive less attention. These techniques are reserved for the most difficult cases where other therapeutic modalities have failed. The American Society of Maxillofacial Surgeons recommends a conservative/non-surgical approach first. Only 20% of patients need to proceed to surgery.
Polysulfated glycosaminoglycan (PSGAG), sold under the brand name Adequan, is an injectable drug for dogs and horses that is used to alleviate the limpness, pain, and lowered range of motion caused by arthritis. It is made of repeat disaccharide units (comprising hexosamine and hexuronic acid), and is similar to glycosaminoglycans already present in the cartilage; PSGAG thus easily integrates itself there. In vitro studies have shown it to inhibit the enzymes that degrade cartilage and bone, as well as suppress inflammation and stimulate the synthesis of replacement cartilage. While it can cause an increased risk of bleeding, it is relatively safe and has a high LD50. PSGAG is one of the most widely prescribed joint treatments for horses.
References
- ↑ Linker A, Meyer K, Hoffman P (April 1960). "The production of hyaluronate oligosaccharides by leech hyaluronidase and alkali". The Journal of Biological Chemistry. 235: 924–7. PMID 14417285.
- ↑ Meyer K, Hoffman P, Linker A (1960). "Hyaluronidases". In Boyer PD, Lardy H, Myrbaumlck K (eds.). The Enzymes. Vol. 4 (2nd ed.). New York: Academic Press. pp. 447–460.
