Invertase amino acids

The most efficient method for the clean hydrolysis of sucrose is by the use of invertase, leading to an equimolar mixture of glucose and fructose (invert sugar). The presence of salts increases the rate of thermal degradation of sucrose.337 The reaction is also possible in the presence of such heterogeneous acidic catalysts as zeolites.338 The hydrolysis of the glycosidic bond is the first step of a number of subsequent reactions that can occur on the glucose and fructose residues, such as dehydrations, combinations with amino acids (Maillard reaction), and many other chemicals or fermentation processes.339... 

By contrast, the amino acid compositions of the two forms of inver-tase (internal and external) differ significantly in the number of residues of certain amino acids. These differences occur notably in the content of serine, alanine, cystine, methionine, tyrosine, lysine, and histidine. The significance of these differences is not yet apparent, but these two invertases are obviously not isoglycoenzymes. The synthesis of proteins having such diverse amino acid compositions as have the two invertases would probably necessitate two separate genetic-control mechanisms. 

The immobilization of invertase on aluminium hydroxide (2) was one of the earliest reports of adsorption technology. The use of aminoacylase adsorbed on DEAE-Sephadex for producing L-amino acids from a racemic mixture of their corresponding ethyl esters (4) was the first industrial application of an immobilized enzyme system. The basic disadvantage of this convenient technique is that binding is weak and the enzyme slowly leaches out. However, for many purposes, this slow leakage is not an important handicap. Immobilizing enzymes by adsorption has been extensively reviewed (5, 6, 27). Some special approaches are described (1, 28-30). 

Table 11.1 Alignment of N-terminal amino acid sequences from A. aculeatus and A. niger fructosyltransferases and invertases.

The availability of metabolites for sucrose synthesis and the need for products of sucrose degradation regulate gene expression. For respiration, sucrose is hydrolyzed by invertase to free glucose and fructose, which are phosphorylated and undergo glycolysis to pyruvate. The pyruvate is then either metabolized by mitochondrial electron transport to ATP and NADH (respiration), or metabolized to provide starting products for amino acid, lipid, and nucleotide syntheses. 

Brown et al. (1984) introduced insertions of three or four amino acids into the yeast invertase signal sequence near its amino terminus. The insertions were predicted to stabilize an a helix, favor a )3 turn, or to destabilize both a-helix and 3-sheet formation. None of these alterations prevented proper secretion of the protein. Thus, the amino-terminal domain of the signal sequence is relatively unconstrained as to conformation. 

Application of site-directed mutagenesis to establish significance of individual amino acids in catalysis has become a common tool in enzymology, although relatively rare with glycoside hydrolases and glycosyltransferases, which are limited to date to studies on /3-galactosidase (136-140), lysozyme (141), and invertase (142). 

Fig. 5.21. Sequence of amino acids 151-200 in S. cerevisiae invertase. The seqnence 174-182 is identical to the peptide fragment seqnenced from MP32 (Moine-Ledoux, et al., 1996)...

Cocoa pulp is composed of (m/m) 82-87% water, 10-15% mono- and disaccharides, 1-5% pectin, 1-3% citric acid, 0.1-0.4% other non-volatile organic acids (e.g., malic acid, oxalic acid, and succinic acid), 0.5-0.7% proteins, and 8-10% minerals and oligoelements (Lehrian and Patterson 1983 Schwan et al. 1995 Barel 1998). Of the mono- and dissacharides present, about 60% is sucrose and 39% is a mixture of fructose and glucose, which are the pulp invertase hydrolysis products of sucrose. The concentration of sucrose, fructose, and glucose is a function of cultivar and fruit age unripe pods contain a higher proportion of sucrose and ripe pods contain mainly fructose and glucose (Lehrian and Patterson 1983 Thompson et al. 2007, 2013). The amino acids, glutamic acid and... 

Yeast invertase,30 32 33 acid phosphatase,29 32 35 37 39 urease,29 /3-glucosi-dase,29 dCMP-amino hydrolase31 and malic enzyme34 36 have been immobilized in gel form on both flat and capillary membranes. Cellulosic and polyamide polymers have been used as supporting membrane matrices. In all instances, immobilized enzymes behave in a manner almost identical to their behavior in homogenous solution, independent of the nature of the polymer. Neither allosteric nor pseudo-allosteric enzymes, proteins whose kinetic behavior is affected by the presence of particular compounds in the reaction environment (ligands), show different kinetic behavior, as they do when subjected to less gentle immobilization procedures.31 34 36... 

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