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The carboxypeptidase A catalyzed hydrolysis of an extensive series of substituted cinnamoyl-L,beta-phenyllactate esters has been investigated. Plots of kcat vs pH are sigmoidal in the pH range 5-9 with an average apparent pKaES of 6.6 +/- 0.1. The values of Km are pH independent in the range pH 5-8. Plots of log kcat/Km vs pH give pKaE values of 6.4 and 9.0 that do not vary significantly through the series. A plot of log kcat (pH 8) vs sigma, the Hammett substituent constant, is linear with a slope rho of 0.5, while log Km vs sigma has a slope of -0.4. The plot of log kcat/Km vs sigma is also linear with rho = 0.9. The Hammett plots are linear at both pH 6 and 8 with closely similar slopes, which indicates that the apparent pKaES near pH 6 does not reflect a change in the rate-determining step. The enzymatic reactions and the nonenzymatic OH- catalyzed hydrolysis reactions are affected alike by changes in the substituent groups; a plot of log kOH, the second-order rate constant for alkaline hydrolysis of the esters, vs log kcat/Km is linear with a slope of 0.9. There is little effect of changing the substituent group in the nonenzymatic pH-independent hydrolysis of the Zn(II) complex of corresponding 4-substituted cinnamic acid 6-carboxypicolinic acid anhydrides (rho < or = 0.1).(ABSTRACT TRUNCATED AT 250 WORDS)

Background The LIM-1863 Cell Line is one of the colon cancer types considered to be responsible for a high rate of deaths, and the glycoalkaloids being natural substances existing in the Solanum species have anticancer effects. Objective This research aims at studying the effect of the glycoalkaloids on viability of the LIM-1863 cancerous cells in-vitro. Materials and Methods The glycoalkaloids in this study are extracted by the ultrasonic waves technique and detecting them by the Thin Layer Chromatography (TLC) in addition to incubating of the LIM-1863 cells with different concentrations of the glycoalkaloids for 48 hours and then assessing of the cell viability using the MTT assay.Results The findings showed that the glycoalkaloids have a toxic effect on the LIM-1863 cells and that half of the inhibiting concentration (IC 50 ) of the Solanum fruits extract: (Solanum nigrum L.), (Solanum villosum Mill.) and (Solanum elaeagnifolium Cav.) on the LIM-1863 cells have the (164.7, 35.91 and 12.14 µg/ml) values successively. Conclusion The observations indicated that the glycoalkaloids are able to inhibit the colon cancer cell proliferation.

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