Enzymatic cleavage derivative

Following the enzymatic cleavage, azaquinone methide was rapidly eliminated and decarboxylation occurred, leading to internal cyclization that released a urea derivative and phenol 35. The latter was disassembled as previously described to generate two equivalents of phenol 36, which was further fragmented to release the four reporter groups. 

Numerous studies have demonstrated that degradation products of (3-carotene exhibit deleterious effects in cellular systems (Alija et al., 2004, 2006 Hurst et al., 2005 Salerno et al., 2005 Siems et al., 2003). A mixture of (3-carotene degradation products exerts pro-apoptotic effects and cytotoxicity to human neutrophils (Salerno et al., 2005 Siems et al., 2003), and enhances the geno-toxic effects of oxidative stress in primary rat hepatocytes (Alija et al., 2004, 2006), as well as dramatically reduces mitochondrial activity in a human leukaemic cell line, K562, and RPE 28 SV4 cell line derived from stably transformed fetal human retinal pigmented epithelial cells (Hurst et al., 2005). As a result of degradation or enzymatic cleavage of (3-carotene, retinoids are formed, which are powerful modulators of cell proliferation, differentiation, and apoptosis (Blomhoff and Blomhoff, 2006). 

The other phospholipids can be derived from phosphatidates (residue = phosphatidyl). Their phosphate residues are esterified with the hydroxyl group of an amino alcohol choline, ethanolamine, or serine) or with the cyclohexane derivative myo-inositol. Phosphatidylcholine is shown here as an example of this type of compound. When two phosphatidyl residues are linked with one glycerol, the result is cardiolipin (not shown), a phospholipid that is characteristic of the inner mitochondrial membrane. Lysophospholipids arise from phospholipids by enzymatic cleavage of an acyl residue. The hemolytic effect of bee and snake venoms is due in part to this reaction. 

Phosphatidylcholine (lecithin) is the most abundant phospholipid in membranes. Phosphatidylethanolamine (cephalin) has an ethanolamine residue instead of choline, and phosphatidylserine has a serine residue. In phosphatidylinositol, phosphatidate is esterified with the sugarlike cyclic polyalcohol myo-inositol. A doubly phosphorylated derivative of this phospholipid, phosphatidylinositol 4,5-bisphosphate, is a special component of membranes, which, by enzymatic cleavage, can give rise to two second messengers, diacylglycerol (DAG) and inositol l,4,5trisphosphate (InsPsi see p.386). 

Tang Y, Feng F, He F, Wang S, Li Y, Zhu D. Direct visuahzation of enzymatic cleavage and oxidative damage by hydroxyl radicals of single-stranded DNA with a cationic pol)4hio-phene derivative. J Am Chem Soc 2006 128 14972-14976. 

Amoxicillin (21) is a semi-synthetic penicillin antibiotic. The penicillin portion is derived from fermentation of either penicillin-V or penicillin-G, and then the sidechain is removed to afford 6-APA. This transformation can be done chemically.69 207 The alternative, which is growing in importance, is to perform an enzymatic cleavage under mild conditions.208 The D-p-hydroxyphenylglycine is then attached as the new sidechain chemical and enzymatic methods are available to achieve this (Scheme 31.16).209 215 The phenylglycine amino acid is obtained by a resolution (Chapters 2, 7, and 25) or by enzymatic hydrolysis of a hydantoin (Chapter 2, 6, and 19).216-220... 

A modification of this approach is the conversion of the e-NHa groups of lysine into dithiocarbamate derivatives by reaction with carbon disulfide at alkaline pH. Figure 29 shows the results of the tryptic digestion of the 20-residue S-peptide before treatment with CS2, after treatment with CS2, and repetition of the enzymatic cleavage after easy removal of CS2 with liberation of the originally blocked t-NH2 group of lysine (Merigan et al., personal communication). 

Heparin is a heterogeneous mixture of anionic sul-fated glycosaminoglycans of 5000-30 000 Da molecular weight commercially derived from bovine lung or porcine intestinal mucosa. Low molecular weight heparins (LMWHs) are specific heparin preparations prepared by chemical or enzymatic cleavage that produce a mixture of products with lower weights of 4000-6000 Da. These mixtures have distinctly different properties from unfractionated heparin. 

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