Lysine reactions

Studies of the MA-lysine reaction by other authors, as discussed previously, were conducted at 37°C or lower. There are a few reports of lysine losses measured as a function of increasing temperature to more than 100°C some of these reports correlate these losses with browning and others with moisture content (21-26). However, most studies of high temperature effects have been on browning rather than nutrient loss. 

Effect of a Glucose-Lysine Reaction Mixture on Protein and Carbohydrate Digestion and Absorption... 

The present study was performed in order to examine whether the compounds in a glucose-lysine reaction mixture per se may influence the digestion and uptake of proteins. Since such an effect was noted, the study was extended to include the digestion and uptake of carbohydrates as well. 

A control diet was prepared as follows Tha labelled egg-white protein was mixed with a basal diet in the proportion 2 98. The basal diet contained 10% casein, 10% sucrose, about 70% starch and 5% maizeoil, as well as vitamins and minerals. A small amount of [sHl-lysine was added to this mixture, giving a ratio of tritium to (11 C) dpm of approximately 10 1. The experimental diet was obtained by adding a small amount ot the glucose-lysine reaction mixture to the control diet. 

Since the glucose-lysine reaction mixture used in this study consisted of a number of different substances, it was of interest to study whether the observed inhibitory effect in vitro could be attributed to some specific compound(s). In order to obtain a separation, an aliquot of the LMW fraction, radiolabel led by [U- glucose added to the reactants, was applied on a Sephadex G-50 column and eluted with water. The UV absorbance was recorded and the eluate was collected in fractions. The degree of inhibition effected by small samples of equal volume from each fraction and exerted on carboxypeptidase A and purified aminopeptidase N was determined as well as the radioactivity... 

Figure 2. Total sugar absorbed from rat intestine at different times after the ingestion of 760 mg sucrose in solution with (U), and without (AJ 8 mg of the high molecular weight (HMW) fraction of the glucose-lysine reaction mixture (IS).

It is clear that the LMW fraction from the glucose-lysine reaction mixture affected, down to a concentration of at least 0.25 mg/ml, the rates of hydrolysis catalyzed by some, but not all, of the enzymes involved in protein digestion in vitro. Car-boxypeptidase A and aminopeptidase N were inhibited by a number of substances in the mixture, some being more effective than others. Efforts to characterize these compounds are in progress. 

S. B. Banks, J. M. Ames, and H. E. Nursten, Isolation and characterisation of 4-hydroxy-2-hydroxymethyl-3-(2 -pyrrolyl)-2-cyclopenten-l-one from a xylose/lysine reaction mixture, Chem. Ind., 1988, 433-434. 

N -Protection of lysine. Reaction with the copper chelate of lysine furnishes the derivative quantitatively. The method is suitable for large-scale preparation. 

Trypsin preferentially catalyzed the condensation of trimethylsilanol under mild conditions (87% HMDS). Subs tial condensation of trimethylsilanol was not observed in the negative control, non-specific protein (i.e. BSA, y-globulins), small molecule (i.e. CaCl2, imidazole, N-methylimidazole), and polypeptide (i.e. poly-L-lysine) reactions in comparison to the raw material (< 1% HMDS). Based on an inqjurity study with small molecule inhibitors (23), the exceptional activity of trypsin and a-chymotrypsin observed in the original enzyme-catalyzed condensation study was soley due to a tryptic impurity. The tertiary... 

Lisinopril can be prepared [29] from the triiiuoroacetamide derivative of lysine. Reaction with phosgene gives the N-carboxyanhydride which reacts with proline. Reductive condensation of the amine is followed by hydrolysis of the triliuoracetamide protective group to give lisinopril. 

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