Hydrolysis and synthesis

Plasteins ate formed from soy protein hydrolysates with a variety of microbial proteases (149). Preferred conditions for hydrolysis and synthesis ate obtained with an enzyme-to-substrate ratio of 1 100, and a temperature of 37°C for 24—72 h. A substrate concentration of 30 wt %, 80% hydrolyzed, gives an 80% net yield of plastein from the synthesis reaction. However, these results ate based on a 1% protein solution used in the hydrolysis step this would be too low for an economical process (see Microbial transformations). 

Gatt, S., 1963, Enzymatic hydrolysis of sphingolipids. 1. Hydrolysis and synthesis of ceramides by an enzyme from rat brain. J. Biol. Chem. 238 3131-3133. 

The above-mentioned facts have important consequences on the stereochemical outcome of the kinetic resolution of asymmetrically substituted epoxides. In the majority of kinetic resolutions of esters (e.g. by ester hydrolysis and synthesis using lipases, esterases and proteases) the absolute configuration at the stereogenic centre(s) always remains the same throughout the reaction. In contrast, the enzymatic hydrolysis of epoxides may take place via attack on either carbon of the oxirane ring (Scheme 7) and it is the structure of the substrate and of the enzyme involved which determine the regioselec-tivity of the attack [53, 58-611. As a consequence, the absolute configuration of both the product and substrate from a kinetic resolution of a racemic... 

In contrast to the hydrolysis and synthesis of ATP connected with proton translocation in mitochondria, chloroplasts and bacterial membranes, the energy linked movement of calcium ions gives rise to the appearance of an acid-stable phosphorylated intermediate in the membranes. A cation specific phosphorylation also occurs in the membranes of the sodium potassium transport system183. However, due to the inability to correlate phosphorylation and ion movement in the latter membranes, membrane phosphorylation has been questioned as being a step in the reaction sequence of ion translocation184,18s. Solely the sarcoplasmic calcium transport system allows to correlate directly and quantitatively ion translocation with the phosphoryl transfer reactions. 

FIGURE 19-21 Catalytic mechanism of F,. (a) 18()-exchange experiment. F, solubilized from mitochondrial membranes is incubated with ATP in the presence of lsO-labeled water. At intervals, a sample of the solution is withdrawn and analyzed for the incorporation of, 80 into the P, produced from ATP hydrolysis. In minutes, the P, contains three or four lsO atoms, indicating that both ATP hydrolysis and ATP synthesis have occurred several times during the incubation, (b) The likely transition state complex for ATP hydrolysis and synthesis in ATP... 

The dedd cells of the mycelium of Rhizopus arrhizus constitute d naturally immobilized lipdse very active in organic solvents. This immobilized enzyme was used for hydrolysis and synthesis of ester bonds triglycerides hydrolysis, and interesterification, esters and glycerides synthesis. More recently, the catalytic system has been applied in drug synthesis to the resolution of racemic esters with a good enantioselectivity. 

Investigation of kinetics of the catalytic process revealed drastic differences in the k, values for reaction in the presence of substoichiometric concentrations of substrate, Mg ATP, occurring in 105-106-fold lower than that in saturating conditions (Allison, 1998). This result clearly indicates strong positive cooperativity of the process. The Allison models for the minimal steps of ATP hydrolysis and synthesis under saturating conditions suggest that catalytic site Fi adopt only two stable conformations, rather than three postulated by Boyer. 

Since the initial work in 1996 from Venton and coworkers on the dynamic screening (under conditions in which both hydrolysis and synthesis occurred in the presence of proteases) of a peptide library for the discovery of novel peptides that bind to fibrinogen [3], many efforts have been made to perform amide exchange in... 

Darroch PI, Dagan A, Granot T, He X, Gatt S, Schuchman EH. A Upid analogue that inhibits sphingomyelin hydrolysis and synthesis, increases ceramide, and leads to cell death. J. Lipid Res. 2005 46 2315-2324. 

FIGURE 5.4 One molecule of water is involved in the hydrolysis and synthesis of ATP, Continued synthesis of ATP during the course of the day docs not result in net production of water in the body This is because ATP is continuously hydrolyzed over the course of the day when it participates in ATP-requiring reactions. 

Robyt JF (1984) Enzymes in the Hydrolysis and Synthesis of Starch. In Whistler RJ, BeMiller JN, Paschall EF (eds) Starch Chemistry and Technology, 2nd edn. Academic Press, New York, pp 102-103... 

H. Al-Rawi and A. Williams, Elimination-Addition Mechanisms of Acyl Group Transfer the Hydrolysis and Synthesis of Carbamates J. Am. Chem. Soc., 1977, 99, 2671. 

Kozak KR, Piusakiewicz JJ, Rowhnson SW, Pmdhomme DR, Marnett LJ (2003) Amino acid determinants in cyclooxygenase-2 oxygenation of the endocannabinoid anandamide. Biochemistry 42 9041-9049 Kurahashi Y, Ueda N, Suzuki H, Suzuki M, Yamamoto S (1997) Reversible hydrolysis and synthesis of anan-... 

Figure 7-21. Time-course data of hydrolysis and synthesis of acetyl-L-alanine using initial conditions as specified in Table 7—3 i11S>.

Fatty acids are absorbed from the bloodstream by adipocytes. Using glycerol-3-phosphate, produced as a by-product of glycolysis, triglycerides are synthesized. Triglycerides are constantly being hydrolyzed and resynthesized in adipocytes. The rates of hydrolysis and synthesis are determined by lipases that are under hormonal control. 

On a final note, it seems necessary to remind that i) several endogenous endocannabinoid(-like) compounds, whose functions are not yet understood, are present in our body, and their biological activity might be affected in unexpected ways by drugs that modulate FAAH or other known proteins of the endocannabinoid system ii) new metabolic enzymes have been recently identified, that catalyze the hydrolysis and synthesis of AEA or 2-AG, and it remains to be elucidated how these multiple pathways may contribute to the overall tone and biological activity of endocannabinoids. 

The mechanisms by which anti-CMH antibodies inhibit fungal growth and/or differentiation remain to be established, but there is a possibility that CMHs are associated with enzymes involved in the hydrolysis and synthesis of the cell wall and / or with GPI-anchored precursors during cell differentiation and division. In this context, binding of antibodies to CMHs could impair the action of CMH-associated functional proteins inhibiting cell wall synthesis. 

The ability of proteinases to catalyze peptide bond hydrolysis and synthesis has long been known [29,30,31,32,33,34], and there is a renewed interest in it in present food protein biochemistry [10,25,27,28,35,36,37,59],... 

Amino-acid Protection. - Carboxyamidomethyl (CAM) esters have been shown to be useful protecting groups in a-chymotrypsin and papain-catalysed peptide hydrolysis and synthesis.5 10 1,3-Dioxans (582) can be obtained from Na-protected serine derivatives by acid-catalysed transacetalation and are sufficiently robust to survive both amino deprotection and peptide coupling reactions. 11 (L)-Histidine benzyl ester can be prepared as the ditosylate salt... 

Calderon-de-la Barca, A.M. R.A. Ruiz-Salazar M.E. Jara-Maarini. Enzymatic hydrolysis and synthesis of soy protein to improve its amino acid composition and functional properties. J. Food Sci. 

Katayama, K., Ueda, N., Katoh, 1., and Yamamoto, S. (1999) Equilibrium in the hydrolysis and synthesis of cannabimimetic anandamide demonstrated by a purified enzyme, Biochimica et Biophysica Acta 1440 205-214. 

Kurahashi, Y, Ueda, N., Suzuki, H., Suzuki, M., and Yamamoto S. (1997) Reversible hydrolysis and synthesis of anandamide demonstrated by recombinant rat fatty-acid amide hydrolase. Biochemical and Biophysical Research Communications 237 512-515. 

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