Characteristics of Lipase Catalysis During Ester Synthesis in Reversed Micellar Systems

The ability of lipase from Candida cylindracea to catalyze ester synthesis from a long chain fatty acid (palmitic acid) and alcohols of varying chain length, is examined. The enzyme is located in the minimal-water environment of reversed micelles. Lipase activity is a strong function of the mode of encapsulation. Direct solid lipase addition to reversed micelles leads to encapsulation in an inactive state unless the enzyme is contacted with the acyl substrate. The alcohol inhibits activity, with low molecular weight alcohols tending to denature the enzyme. Implications to reversed micelle based biocatalyst preparation are briefly discussed.     

Characterization of MCF 7 breast cancer cell growth inhibition by the antiestrogen nitromifene (CI 628) and selected metabolites

Besides undergoing O-demethylation in vivo, the triarylethylene antiestrogen nitromifene [1-(4-(2-pyrrolidinylethoxy)phenyl)-1-(4-methoxy)-phenyl-2-phenyl- 2- nitroethene, 1] undergoes biotransformation via nitroreduction, ethene bond cleavage, and pyrrolidine ring oxidation affording ketone metabolites 2 and 3 and a lactam metabolite 4. Estrogen receptor (ER) affinities of 1, 2, and 4 were, in turn, 1.7, 0.1, and 3.8% that of estradiol in MCF 7 human breast cancer cells, and these compounds inhibited by 50% the proliferation of MCF 7 cells at respective concentrations of 1.1, 5.6, and 2.0 microM. The inhibitory effect of 4 was fully reversible by estradiol, but that of 2 was only partially reversible. Also 3, which did not interact with ER, inhibited proliferation by 44% at a concentration of 10 microM. These results suggested that in contrast to 4, the effects of 2 and 3 were due in part to interaction with sites distinct from ER. Antiestrogen binding sites and calmodulin have been suggested to mediate antiproliferative effects of drugs. Interaction of ligands with the former sites has been proposed to antagonize the growth promoting effect of histamine. Although 2 and 3 had high affinities for these sites, their inhibitory effects on MCF 7 cell growth were largely unaffected by the presence of histidine, the source of intracellular histamine. Thus, the relationship between antiestrogen binding site affinity and antiproliferative effects of 2 and 3 was not clarified. In contrast, MCF 7 cell growth suppression potencies paralleled calmodulin antagonist potencies of 1 and 2 suggesting that interaction of 1 and 2 with calmodulin may contribute to their anticancer effects.     

Mobility of salivary components as a possible reason for differences in the responses of alfalfa to the spotted alfalfa aphid and pea aphid

The spotted alfalfa aphid (SAA), Therioaphis trifolii maculata (Buckton), causes a characteristic veinal chlorosis and necrosis in the growing tips of susceptible cultivars of alfalfa. The pea aphid, Acyrthosiphon pisum (Harris), causes general degenerative changes in alfalfa but no specific, local symptoms. Biochemical and electrophoretic analyses detected similar enzymes in the ejected saliva of either species: pectin methylesterase, endopolygalacturonase and at least three isozymes of a copper dependent oxido-reductase that showed both catechol oxidase and peroxidase activity. Pectinase and catechol oxidase activities per unit of soluble protein were much greater in the saliva of pea aphid compared with that of SAA. The isozymes of the oxidase from SAA were roughly half the molecular weights of the corresponding isozymes from pea aphid, however, and radiotracer studies showed that soluble secretions injected into alfalfa by SAA travelled to growing tips considerably faster than the secretions of pea aphid. It is suggested that differences in the lesions caused by these aphids may be due to reaction kinetics rather than specific salivary toxins; that the rate of arrival of salivary components, possibly the oxidases, at phloem unloading sites may determine whether the plant's local defensive system is able to repress the immediate challenge or undergoes a run-away reaction leading to necrosis.