Alpha cleavage mechanism

Fig. 3. The role of FKN/CX3R1 in inducing atherosclerosis may involve two mechanisms. The first is the release of soluble FKN through cleavage of membrane-expressed FKN by TNF-alpha converting enzyme (TACE). Soluble FKN is then able to attract circulating monocytes and effector T cells expressing CX3CR1. The second mechanism is that of firm adhesion of circulating cells to membrane-bound FKN.

A possible mechanism for the cleavage may involve the formation of an olefin-metal complex intermediate in which the silicon atom alpha to the vinyl group would be vulnerable to the attack of ethanol. 

Shyadehi, A.Z., D.C. Lamb, S.L. Kelly, D.E. Kelly, W.H. Schunck, and J.N. Wright et al. (1996). The mechanism of the acyl-carbon bond cleavage reaction catalyzed by recombinant sterol 14a-demethylase of Candida albicans (other names are Lanosterol 14 alpha-demethylase, P-45014DM, and CYP51). J. Biol. Chem. 271, 12445-12450. 

Akhtar M, Corina D, Miller S, Shyadehi AZ, Wright JN (1994) Mechanism of the acyl-carbon cleavage and related reactions catalyzed by multifunctional P-450s studies on cytochrome P-450(17)alpha. Biochemistry 33 4410-4418... 

B. W. Murray, V. Wittmann, M. D. Burkart, S. C. Hung, C. H. Wong, Mechanism of human alpha-l,3-fucosyItransferase V glycosidic cleavage occurs prior to nucleophilic attack. Biochemistry, (1997), 36, 823-31. 

An elucidation of the mechanisms of brain iron homeostasis, as outlined in figure 1, will help our understanding of AD especially since iron binds to Ap-peptide and enhances beta-amyloid toxicity [35-38]. Excess iron accumulation is a consistent observation in the AD brain. As discussed above, patients with hemochromatosis are at risk developing AD at an earlier age [2]. Brain autopsy samples from AD patients have elevated levels of ferritin iron, particularly in the neurons of the basal ganglia [39] and most amyloid plaques contain iron and ferritin-rich cells [40]. Clinically there is a reported decrease in the rate of decline in AD patients who were treated with the intramuscular iron chelator, desferrioxamine [41]. Iron enhances cleavage of the Ap-peptide domain of APP by the metalloprotease alpha secretase [42, 43]. Part of the protective effect of the major cleavage product of APP, APP(s), may derive from its capacity to scavange metals to diminish metal-catalyzed oxidative stress to neuronal cells [44]. APP is, itself, a metalloprotein [4]. 

According to Wall and co-workers [2] the pyrolysis of polyethylene proceeds by a radical chain mechanism. The products formed result from the process of random-chain cleavage, followed by intermolecular or intramolecular hydrogen abstraction. Hydrogen abstraction occurs preferentially at tertiary carbon atoms, and product formation results from homolysis of the carbon-carbon bond at the beta position relative to the radical site. The major products formed are the -alkanes and alpha-omega-diolefins. The peaks between the triplets result from chain branching. 

Kalsheker NA, Beam S, Chambers L, Sreedharan S, Brocklehurst K, Lomas DA. The house dust mite allergen Der p 1 catalytically inactivates alpha 1-antitrypsin by specific reactive centre loop cleavage a mechanism that promotes airway inflammation and asthma. Biochem Biophys Res Commun 1996 221 59-61. 

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