Intracellular estimating

Km for an enzymatic reaction are of significant interest in the study of cellular chemistry. From equation 13.19 we see that Vmax provides a means for determining the rate constant 2- For enzymes that follow the mechanism shown in reaction 13.15, 2 is equivalent to the enzyme s turnover number, kcat- The turnover number is the maximum number of substrate molecules converted to product by a single active site on the enzyme, per unit time. Thus, the turnover number provides a direct indication of the catalytic efficiency of an enzyme s active site. The Michaelis constant, Km, is significant because it provides an estimate of the substrate s intracellular concentration. 

Neisseria gonorrhoeae is a gram-negative diplococcus estimated to cause up to 600,000 infections per year in the United States. Humans are the only known host of this intracellular parasite. 

A final optical application deals with the measurement of intracellular nicotinamide adenine dinucleotide (NADH) by fluorescence [77], giving information about the physiological status of wastewater treatment plant biomass. This indirect method could be envisaged for toxicity estimation. 

From a theoretical perspective, and provided that the network structure and some information about input and output fluxes are available, the intracellular steady-state fluxes can be estimated utilizing flux balance analysis. In conjunction with large-scale concentrations measurements, as described in Section IV, this allows, at least in principle, to specify the metabolic state of the system. 

As discussed in Section V.B, flux balance analysis allows to estimate intracellular steady-state fluxes provided the network structure and some information about... 

R. Krapf, C. A. Berry, and A. S. Verkman, Estimation of intracellular chloride activity in isolated perfused rabbit proximal convoluted tubules using a fluorescent indicator, Biophys. J. 53, 955-962 (1988). 

Much of industrial chemistry takes place in organic solvents, or involves apolar compounds. Biocatalysis, in contrast, typically involves aqueous environments. Nevertheless, enzymes and microorganisms do in fact encounter apolar environments in Nature. Every cell is surrounded by at least one cell membrane, and more complex eukaryotic cells contain large amounts of intracellular membrane systems. These membranes consist of lipid bilayers into which many proteins are inserted present estimates, based on genomic information, are that about one-third of all proteins are membrane proteins, many of which are so-called intrinsic proteins that are intimately threaded through the apolar bilayer. These proteins are essentially dissolved in, and function partly within, an apolar phase. 

The extracellular glucose concentration in the brain of the rat is about 0.5 mmol/L whereas the intracellular concentration is estimated to be 2 mmol/L. Since there is no active transport into the brain, some form of com-partmentation of glucose must exist. 

A radiometric technique for estimating the rates of intracellular synthesis and/or turnover of a metabolite. To measure the rates of synthesis, cells are exposed to a radioisotopically labeled precursor (such as pH]-,... 

To make quantitative predictions of DDI for the new compound as perpetrator, a reliable estimate of a relevant in vivo concentration is needed. What is tmly needed is knowledge of the concentration of the inhibitor available to bind to the enzyme. For liver, if the well accepted free-dmg hypothesis (which underwrites fundamental drug action principles in pharmacology) is applied for DDI, then the use of a free intracellular liver concentration is needed. For inhibitors that are permeable through membranes, the free concentration in the portal vein should serve as the closest proxy for free intracellular concentration in the liver. Diminished permeability as well as active uptake and efflux from liver cells can confound this relationship. Nevertheless, use of estimates of unbound portal vein concentrations (which can be estimated from... 

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