Multiple attack

Vmax and Km values using pga as a substrate at the optimum pH 4.1 were calculated as 500 U/mg and 0.15 mg/ml and 2000 U/mg and 0.15 mg/ml for PGI and PGII, respectively. Mode of action analysis revealed a random cleavage pattern for PGII while for PGI multiple attack on a single chain was observed. For PGII a partial subsite map was obtained. 

Dicke M, van Loon JJA, Soler R (2009) Chemical complexity of volatiles from plants induced by multiple attack. Nat Chem Biol 5 317-324... 

Although some depolymerases act processively in cleaving their polymeric substrates, others act by what can be described as multiple attack which results in nonselective scission or random scission. The analysis of cleavage products during the course of enzyme-catalyzed depolymerization can provide important clues about the nature of the reaction. With random scission, the rate of bond scission must be proportional to the total number of unbroken bonds present in the solution. Thomas measured the rate of base addition in a pH-Stat (a device with an automated feedback servomotor that expels ti-trant from a syringe to maintain pH) to follow the kinetics of DNA bond scission by DNase. The number of bonds cleaved was linear with time, and this was indicative of random scission. In other cases, one may apply the template challenge method to assess the processivity of nucleic acid polymerases. See Processivity... 

SHIELDING MULTI ENZYME Multiple attack enzyme,... 

NSPORT metal ion EXCHANGE TIMES MICROENVIRONMENT MULTIPLE ATTACK UCLEOPHILIC SUBST TUTION REACTION NONLINEAR INHIBITION RANDOM SCISSIOI VTE MFC MYOGLOBIN OXYGENATION NUCLEATION ONE DIMENSIONA... 

The procedure for synthesizing sulfanilamide (a sulfa drug) is a multistep procedure as illustrated in Figure 13-50. The first step also works if you substitute an acyl chloride for the acid anhydride. The conversion of the amine to an amide converts the strong activator into a medium activator, limiting multiple attacks. The last step converts the amide back into an... 

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. 

Multidrug resistance protein 417 Multilamellar vesicles (liposomes) 392 Multiple attack concept 606 Multisubstrate enzymes, kinetics of 464 Muramic acid (Mur) 165s Murein 170,428,429s. See also Peptidoglycan Musci 29 Muscle(s)... 

However, applying extraction by solvent to the nuclear field is not an easy task for the solvent that undergoes multiple attacks—chemical, thermal, but especially radiolytic. This multiplicity is reinforced by the biphasic nature of the chemical system and the presence of numerous solutes, be it in aqueous or organic phase. Radiolysis of such a system thus leads to the formation of a multitude of radicals and ionized species (including the reactive species II-, OH-, solvated electrons, H2, or H202), which recombine in molecular products shared between the two phases. 

In the 1998 DARPA intrusion detection evaluation program, an environment was set up to acquire raw TCP/IP dump data for a network by simulating a typical U.S. Air Force LAN. The LAN was operated like a true environment, but being blasted with multiple attacks [13]. In 1999 sample data set of network traffic was presented at KDD 99 conference [14]. 

A. oryzae a-amylase has about the same degree of multiple attack as human salivary a-amylase, i.e. an average of three hydrolytic cleavages per chain encounter. A. oryzae a-amylase is the only common a-amylase known to hydrolyze the cyclic a-(l- 4)-l inked maltodextrins to any extent.25,26 A kinetic analysis revealed that the catalytic constant, k2, increased significantly from 3.3 to 270 to 3270min-1 for cyclomaltohexaose, cyclomaltoheptaose and cyclomalto-octaose, respectively, while the Km was 4.7 M, 10.2 M and 2.4 M, respectively.26... 

The active-sites of the glucoamylases are pockets that do not have a flexible, mobile loop that can act as a trap door to let the product (glucose) out. After the glycosidic bond is cleaved by glucoamylase, the remaining starch chain must dissociate and leave the active-site before glucose can leave. This explains why glucoamylase has such a low turnover number, and why it does not have a multiple attack mechanism. 

Necrotizing IK, a chronic form of HSK, may occur after multiple attacks. It is characterized by a white, dense. 

Also, the bond second from the reducing end (bond 10) is believed to be readily split.The high yields of maltose may be obtained by a preferential attack on bond 10, or by a degree of multiple attack. Calculations of theoretical yields to be expected on the basis of preferential attack on bond 10 are in fairly good agreement with experiment, whereas those based on multiple attack predict more maltose than is actually formed. 

Mammalian aipha-amylases probably attack large substrates by a multiple-attack mechanism, but it seems unlikely that any of the other well studied types of alpha-amylase act in this way. 

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