Isozymes, number

Conventional and novel PKC isozymes are potently activated by phorbol esters, heterocyclic compounds found in the milky sap exuded by plants of the Euphorbiaccae family. This sap was used medicinally as a counterirritant and cathartic agent over the millennia we now know that the active ingredients, phorbol esters, specifically bind to the Cl domain, the diacylglycerol sensor described above. In fact, their ability to recruit PKC to membranes is so effective that phorbol esters cause maximal activation of conventional PKCs, bypassing the requirement for Ca2+. This module is found in a number of other proteins in addition to PKC, so the profound effects of phorbol esters on cells are mediated by other proteins in addition to PKC. 

Estimated based on published protein expression (19) and converted to total number of subunit active sites per g of liver tissue. The Michaelis-Menton parameters for ethanol oxidation at pH 7.5 were utilized to calculate individual isozyme activities as a total activity per g of tissue and then normalized as a percent of total activity per pg of tissue following summation of all isozyme activities... 

As indicated in Table 2.1, most of the promoters used in plant tissue culture have been based on the constitutive cauliflower mosaic virus (CaMV) 35S promoter. In contrast, inducible promoters have the advantage of allowing foreign proteins to be expressed at a time that is most conducive to protein accumulation and stability. Although a considerable number of inducible promoters has been developed and used in plant culture applications, e.g. [32-37], the only one to be applied thus far for the production of biopharmaceutical proteins is the rice a-amylase promoter. This promoter controls the production of an a-amylase isozyme that is one of the most abundant proteins secreted from cultured rice cells after sucrose starvation. The rice a-amylase promoter has been used for expression of hGM-CSF [10], aranti-trypsin [12, 29, 38, 39] and human lysozyme [30]. 

To date, there have only been a limited number of studies directly examining PKC in bipolar disorders [77], Although undoubtedly an oversimplification, particulate (membrane) PKC is sometimes viewed as the more active form of PKC, and thus an examination of the subcellular partitioning of this enzyme can be used as an index of the degree of activation. Friedman etal. [78] investigated PKC activity and PKC translocation in response to serotonin in platelets obtained from bipolar-disorder patients before and during lithium treatment. They reported that the ratios of platelet-membrane-bound to cytosolic PKC activities were elevated in the manic patients. In addition, serotonin-elicited platelet PKC translocation was found to be enhanced in those patients. With respect to brain tissue, Wang and Friedman [74] measured PKC isozyme levels, activity and translocation in postmortem brain tissue from patients with bipolar disorder, and reported increased PKC activity and translocation in the brains of bipolar patients compared with controls, effects which were accompanied by elevated levels of selected PKC isozymes in cortices of bipolar disorder patients. 

Peroxidases are widely distributed enzymes in the plant kingdom. Despite their ubiquity and the ever-increasing number of functions ascribed to them, the precise role and localization of the many isozymes remain uncertain... 

One of the difficulties of peroxidase studies is that the enzymes can react with a number of synthetic or natural substrates and that even the use of purified isozymes in assays for substrate specificity does not identify any definitive roles. A search for specific inhibitors represents another approach which is still poorly developed despite its potential utility. 

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