Enzymes and hydrolysis

Pacsu4 5 has suggested a structure for starch involving a small number of non-cyclic hemiacetal linkages, the number being presumably sufficient to account for the number of endgroups determined by the methylation method. Halsall, Hirst and Jones6 have commented on this structure, however, and have shown it to be incompatible with the results of periodate-oxidation studies. In addition, these authors pointed out that it would be difficult to explain enzymic hydrolysis and dextrin formation on the basis of such a structure. 

The investigations carried out by Professor French and his students were based on sound experimental approaches and on intuitive theoretical considerations. The latter often resulted in new experiments for testing a hypothesis. On the basis of theoretical considerations, Professor French proposed a model for the structure of the amylopectin molecule, and the distribution of the linear chains in this molecule. This model was tested by utilizing enzymes that selectively cleave the linear chains, and the results substantiated the theoretical deductions. He proposed a theory on the nature and types of reactions occurring in the formation of the enzyme - starch complex during the hydrolysis of starch by amylases. In this theory, the idea of multiple attack per single encounter of enzyme with substrate was advanced. The theory has been supported by results from several types of experiments on the hydrolysis of starch with human salivary and porcine pancreatic amylases. The rates of formation of products, and the nature of the products of the action of amylase on starch, were determined at reaction conditions of unfavorable pH, elevated temperatures, and increased viscosity. The nature of the products was found to be dramatically affected by the conditions utilized for the enzymic hydrolysis, and could be accounted for by the theory of the multiple attack per single encounter of substrate and enzyme. 

The effectiveness of estriol determinations is reduced by hydrochlorothiazide when acid hydrolysis was used. When glucuronidase hydrolysis was used along with internal standards, the effect of hydrochlorothiazide was overcome. There is no difference between enzyme hydrolysis and acid hydrolysis over the clinically important range of 0-10 mg/24 hr. 

Other researchers have used very similar enzyme hydrolysis and extraction methods followed by GC without further purification. This is preferred when possible because of the time saved and the decreased chance for sample loss due to manipulation. Many of these procedures are nearly identical, and it is often just a matter of choosing the one which is preferred. 

CATALYSIS WITH IMMOBILIZED ENZYMES HYDROLYSIS AND ESTERIFICATION BY RHIZOPUS ARRHIZUS... 

Presence of native starch crystals. In plant materials, starch exists as semicrystalline, granular entities. Starch molecules, both amy-lose and amy lopectin, with their many intermo-lecular hydrogen bonds, give structure to the starch granule (Zobel, 1988). The crystalline regions formed by this intermolecular hydrogen bonding are somewhat resistant to enzyme hydrolysis and need to be broken prior to enzyme treatments. 

S. Peat, J. R. Turvey, and J. M. Evans, The structure of floridean starch. Part II. Enzymic hydrolysis and other studies,./. Chem. Soc. (1959) 3341-3344. 

Hartwick (C12) also used RPLC to separate oligonucleotides and then used enzyme hydrolysis and subsequent RPLC chromatography of the nucleoside fragments for determination of the structures of the oligonucleotides. 

Modulators of Endocannabinoid Enzymic Hydrolysis and Membrane Transport... 

Fig. 5. Thin-layer silica-gel chromatography of an extract of umbilical cord plasma after enzyme hydrolysis and a further extract obtained after solvolysis. The chromatogram was developed once in the system benzene-ethyl alcohol (95 5 v/v) and twice in the system cyclohexane-ethyl acetate (50 50 v/v). Color development was by spraying with antimony trichloride with subsequent heating.

As shown Figure (10), the antitumor activity of ARS-2 was sensitive to proteolysis, but resistant to enzyme hydrolysis and periodate oxidation of the carbohydrate moiety, suggesting that the protein moiety is necessary for the antitumor activity of ARS-2 [33]. 

Figure 3 The different fates of three acyl enzymes the -o-Ala-o-Ala derived PBP o-Ala acyl-enzyme (transpeptidation) the penicillin-derived /3-lactamase acyl-enzyme (hydrolysis) the /3-lactamase inactivator-derived /3-lactamase acyl-enzyme (hydrolysis and fragmentation to stable acyl-enzymes).

A. Classification All penicillins are derivatives of 6-aminopenicillanic acid and contain a beta-lactam ring structure that is essential for antibacterial activity. PeniciUin subclasses have additional chemical substituents that confer differences in antimicrobial activity, susceptibility to acid and enzymic hydrolysis, and biodisposition. 

In connection with the toxicity of the pyrrolizidine alkaloids the toxic effects of the alkaloids themselves have been reproduced by dosing experimental animals with synthetic compounds. Because the most toxic alkaloids are esters which are resistant to enzymic hydrolysis, and which are converted in vivo into pyrrole derivatives, it was expected that simpler pyrroline esters would prove to exhibit the same toxic properties as the alkaloids. This expectation was realised when it was shown that the dicarbamate (59) is rather more toxic than monocrotaline, and further that the tissue damage produced is histologically similar to that observed in cases of pyrrolizidine alkaloid poisoning. A compound of slightly lesser toxicity is the retronecine derivative (60). 

A systematic identification scheme, based on paper chromatography and t.l.c., acidic and enzymic hydrolysis, and the reaction of carbohydrates with several location reagents, has been applied to the analysis of oligosaccharides present in the urine and faeces of sick children and in the diets they are fed. The identity and origin of these oligosaccharides is described and their relevance to the diagnosis and treatment of children with suspected disorders of carbohydrate metabolism is discussed. 

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