Enzymes plasma

Use of the plasma enzyme creatine kinase Mb (CK-MB) in the diagnosis of myocardial infarction. 

Use of the plasma enzyme alanine aminotransferase (ALT) in monitoring the progress of infectious hepatitis. 

Certain enzymes, proenzymes, and their substrates are present at all times in the circulation of normal individuals and perform a physiologic function in the blood. Examples of these functional plasma enzymes include lipoprotein Upase, pseudocholinesterase, and the proenzymes of blood coagulation and blood clot dissolution (Chapters 9 and 51). The majority of these enzymes are synthesized in and secreted by the liver. 

Plasma also contains numerous other enzymes that perform no known physiologic function in blood. These apparently nonfunctional plasma enzymes arise from the routine normal destruction of erythrocytes, leukocytes, and other cells. Tissue damage or necrosis resulting from injury or disease is generally accompanied by increases in the levels of several nonfunctional plasma enzymes. Table 7-2 lists several enzymes used in diagnostic enzymology. 

Assay of plasma enzymes aids diagnosis and prognosis. For example, a myocardial infarction elevates serum levels of lactate dehydrogenase isozyme I,. 

HDL is synthesized and secreted from both liver and intestine (Figure 25—5). However, apo C and apo E are synthesized in the liver and transferred from fiver HDL to intestinal HDL when the latter enters the plasma. A major function of HDL is to act as a repository for the apo C and apo E required in the metabohsm of chylomicrons and VLDL. Nascent HDL consists of discoid phosphohpid bilayers containing apo A and free cholesterol. These hpoproteins are similar to the particles found in the plasma of patients with a deficiency of the plasma enzyme lecithimcholesterol acyltransferase (LCAT) and in the plasma of patients with obstructive jaundice. LCAT—and the LCAT activator apo A-I— bind to the disk, and the surface phosphohpid and free cholesterol are converted into cholesteryl esters and... 

Trichloroethylene may occur in drinking water along with other chlorinated hydrocarbons, so effects of these chemicals in combination are of interest to public health. Hepatotoxicity, as measured by plasma enzyme activity, was increased synergistically in rats by oral administration of carbon tetrachloride combined with trichloroethylene (Borzelleca et al. 1990). In addition, synergistic effects were implicated in a 3-day study in... 

Liver contained 156 (68-563) pg PCB 126/kg FW pronounced liver enlargement lymphoid depletion of spleen 10-fold increase in hepatic microsomal EROD and benzyoxyresorufin-O-dealkylase 5-fold increase in methoxyresorufin-O-dealkylase Liver had 380 pg PCB 126/kg FW with increasing necrosis above effects plus decreased bone growth, decreased spleen weight, and degenerative lesions of thyroid Liver had 1.1 (0.6-4.5) mg PCB 126/kg FW above effects plus decreased body weight, decreased hepatic thiol concentrations, and increased plasma enzyme activities... 

Statistical Methods. Means of treatment groups for plasma retention of BSP, plasma osmolality, total plasma protein concentration and urine flow rates were compared by students t test for independent sample means (17). Plasma enzyme activity data were converted to a quantal form and analyzed by the Fischer Exact Probability Test (18). Values greater than 2 standard deviations (P < 0.05) from the control value were chosen to indicate a positive response in treated fish. 

There was a trend for hydrolysis by plasma enzymes to increase with increasing polarity of the substituent, or, more precisely, with the polar surface area of the substituent. 

Borzelleca JF, OHara TM, Gennings C, et al. 1990. Interactions of water contaminants. I. Plasma enzyme activity and response surface methodology following gavage administration of CC14 and CHC13 or TCE singly and in combination in the rat. Fundam Appl Toxicol 14 477-490. 

Thawed samples Low glucose and protein and loss of plasma enzyme activities... 

A. Alteration of plasma enzyme levels in disease states... 

Some enzymes show relatively high activity in only one or a few tissues. The presence of increased levels of these enzymes in plasma thus reflects damage to the corresponding tissue. For example, the enzyme alanine aminotransferase ALT, see p. 248) is abundant in the liver. The appearance of elevated levels of ALTin plasma signals possible damage to hepatic tissue. Increases in plasma levels of enzymes with a wide tissue distribution provide a less specific indication of the site of cellular injury. This lack of tissue specificity limits the diagnostic value of many plasma enzymes. 

Esterification of cholesterol When cholesterol is taken up by HDL, it is immediately esterified by the plasma enzyme phos-phatidylcholine cholesterol acyltransferase (PCAT, also known as LCAT, in which "L" stands for lecithin). This enzyme is synthesized by the liver. PCAT binds to nascent HDLs, and is activated by apo A-l. PCAT transfers the fatty acid from carbon 2 of phosphatidyl-... 

Reasons for the presence of enzymes in the plasma Enzymes can normally be found in the plasma either because they were specifically secreted to fulfill a function in the blood, or because they were released by dead or damaged cells. Many diseases that cause tissue damage result in an increased release of intracellular enzymes into the plasma. The activities of many of these enzymes (for example, creatine kinase, lactate dehydrogenase, and alanine aminotransferase) are routinely determined for diagnostic purposes in diseases of the heart, liver, skeletal muscle, and other tissues. 

Poly-C-SpecificRibonuclease (P-RNase) (EC3.1.27.5). Warshawand Fournier (W3) showed that an increase in plasma enzyme activity of pancreatic P-RNase in patients with AP may indicate necrotic lesions, and is one of the few direct markers of pancreatic tissue injury (Nl, W4). Due to the time-consuming and cumbersome nature of the P-RNase assay procedure and the development of effective visualization techniques providing direct information on the structure of the inflamed pancreas, the diagnostic utility of the P-RNase assay has not been extensively studied (Table 3). 

The mechanism of action of DFO is the formation of a stable complex with iron. It prevents the iron from entering into further chemical reactions, It is important that DFO chelates iron from hemosiderin and ferritin, but not from transferrin, It does not bind with the iron from hemoglobin and cytochromes. It is theorized that DFO is metabolized by plasma enzymes. The chelate is soluble in water and passed easily through the kidney (reddish color of urine). 

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