Cleaving eggs

MacLean, S. A., A. C. Longwell. and W. J. Blogoslawski. Effects of ozone-treated sea water on the spawned, fertilized, meiotic, and cleaving eggs of the commercial American oyster. Mutat. Res. 21 283-285, 1973. 

Spirin and Nemer (1965) have also observed the postribosomal components in homogenates of cleaving eggs, blastulae, and gastrulae of sea urchins and Nemer and Infante (1965) found them to contain nonribosomal RNA s similar to those extracted from the polyribosomes. In addition these workers report that the labeled RNA from the postribosomal region has a very high capacity for hybridizing with the sea urchin DNA. 

Lysozyme is an enzyme that hydrolyzes polysaccharide chains. It ruptures certain bacterial cells by cleaving the polysaccharide chains that make up their cell wall. Lysozyme is found in many body fluids, but the most thoroughly studied form is from hen egg whites. The Russian scientist P. Laschtchenko first described the bacteriolytic properties of hen egg white lysozyme in 1909. In 1922, Alexander Fleming, the London bacteriologist who later discovered penicillin, gave the name lysozyme to the agent in mucus and tears that destroyed certain bacteria, because it was an enzyme that caused bacterial lysis. 

Lysozyme, extracted from egg whites, is an enzyme that cleaves bacterial cell walls. A 20.0-mg sample of this enzyme is dissolved in enough water to make 225 mL of solution. At 23°C the solution has an osmotic pressure of 0.118 mm Hg. Estimate the molar mass oflysozyme. 

Hen egg-white lysozyme catalyzes the hydrolysis of various oligosaccharides, especially those of bacterial cell walls. The elucidation of the X-ray structure of this enzyme by David Phillips and co-workers (Ref. 1) provided the first glimpse of the structure of an enzyme-active site. The determination of the structure of this enzyme with trisaccharide competitive inhibitors and biochemical studies led to a detailed model for lysozyme and its hexa N-acetyl glucoseamine (hexa-NAG) substrate (Fig. 6.1). These studies identified the C-O bond between the D and E residues of the substrate as the bond which is being specifically cleaved by the enzyme and located the residues Glu 37 and Asp 52 as the major catalytic residues. The initial structural studies led to various proposals of how catalysis might take place. Here we consider these proposals and show how to examine their validity by computer modeling approaches. 

Privalov et al (1989) studied the unfolded forms of several globular proteins [ribonuclease A, hen egg white lysozyme, apomyoglobin (apoMb), cytochrome c, and staphylococcal nuclease]. Unfolding was induced by 6 M Gdm-HCl at 10°C, heating to 80°C, or by low pH at 10°C with cross-links cleaved (reduction and carboxamidomethylation or removal of heme). The unfolded forms showed CD spectra (Fig. 27)... 

Polysaccharide chains in the peptidoglycan layer (Fig. 8-29) of the cell walls of bacteria are attacked and cleaved by lysozymes,55 enzymes that occur in tears and other body secretions and in large amounts in egg white. Some bacteria and fungi, and even viruses, contain lysozymes.56 Their function is usually to protect against bacteria, but lysozyme of phage T4 is a component of the baseplate of the virus tail (Box 7-C). 

At this point there s a little twist to our developing chicken-and-egg scenario. Even activated Stuart factor can t turn on prothrombin. Stuart factor and prothrombin can be mixed in a test tube for longer than it would take a large animal to bleed to death without any noticeable production of thrombin. It turns out that another protein, called accelerin, is needed to increase the activity of Stuart factor. The dynamic duo—accelerin and activated Stuart factor— cleave prothrombin fast enough to do the bleeding animal some good. So in this step we need two separate proteins to activate one proenzyme. 

Protease is by far the most widely used of all detergent enzymes. Introduced in the 1960s, it has since become one of the more important components of detergent formulations [6]. Proteases aid in the removal of many soils commonly encountered by the consumer, such as food stains (cocoa, egg yolk, meat), blood, and grass. This enzyme hydrolyzes or breaks up the peptide bonds found in proteins resulting in the formation of smaller and more soluble polypeptides and amino acids. Since most enzymes have to function under high pH conditions, subtilisin, a bacterial alkaline protease, is commonly used in laundry detergents. This particular protease does not hydrolyze any specific peptide bond in proteinaceous stains but cleaves bonds in a somewhat random manner. 

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