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• 55-40-3 alpha-methyldopa 

Relevant academic research and scientific papers

Screening test for insecticides interfering with cuticular sclerotization

The potential of known and new insecticides to interfere with cuticle sclerotization was investigated using assays for key enzymes such as phenoloxidase, quinone methide isomerase and DOPA decarboxylase. Homogenates from the blowfly Lucilia cuprina and from the epithelial cell line from Chironomus tentans were used to examine the compounds under investigation. Phenoloxidases are known to oxidize DOPA, the substrate for DOPA decarboxylase. Since phenoloxidases were not detectable in C. tentans cell homogenates, inhibitor and kinetic studies were done for comparison with DOPA decarboxylase of this insect cell line. DOPA decarboxylase and phenoloxidase of L. cuprina exerted highest specific activities at early pupal stages (day 7). The apparent K(m) values for the two enzymes were 0.47(±0-21) mM and 0.71(±0.16) mM, respectively, using L-DOPA as substrate. DOPA decarboxylase from C. tentans had a K(m) value of 0.42(±0.18) mM. Quinone methide isomerase was most active in young pupae. In terms of substrate specificity for enzymic (mushroom-tyrosinase) production of different quinones from their corresponding catechols, that with dopamine quinone proved to be the most efficient. Synthesis of derivatives of L-DOPA and L-tyrosine led to a compound which inhibited both phenoloxidase and quinone methide isomerase. DOPA decarboxylase from L. cuprina and from cells of C. tentans was inhibited by carbidopa (IC50 values of 0.021(±0.011) μM and 0.031(±0.019) μM, respectively) and indomethacine (IC50 values of 22.6(±7.1) μM and 18.8(±9.7) μM). Both compounds exerted a competitive type of inhibition and were able to interfere with development of L. cuprina.

Stereospecificity of mushroom tyrosinase immobilized on a chiral and a nonchiral support

Mushroom tyrosinase was immobilized from an extract onto glass beads covered with the cross-linked totally cinnamoylated derivates of D-sorbitol (sorbitol cinnamate) and glycerine (glycerine cinnamate). The enzyme was immobilized onto the support by direct adsorption, and the quantity of immobilized tyrosinase was higher for sorbitol cinnamate, the support with the higher number of esterified hydroxyls per unit of monosacharide, than for glycerine cinnamate. The results obtained from the stereospecificity study of the monophenolase and diphenolase activity of immobilized mushroom tyrosinase are reported. The enantiomers L-tyrosine, DL-tyrosine, D-tyrosine, L-dopa, DL-dopa, D-dopa, L-α-methyldopa, DL-α-methyldopa, L-isoprenaline, DL-isoprenaline, L-adrenaline, DL-adrenaline, L-noradrenaline, and D-noradrenaline were assayed with tyrosinase immobilized on a chiral support (sorbitol cinnamate), whereas L-tyrosine, DL-tyrosine, D-tyrosine, L-dopa, DL-dopa, D-dopa, L-α-methyldopa, and DL-α-methyldopa were assayed with tyrosinase immobilized on a nonchiral support (glycerine cinnamate). The same Vmaxapp values for each series of enantiomers were obtained. However, the Kmapp values were different, the L isomers showing lower values than the DL isomers, whereas the highest K mapp value was obtained with D isomers. No difference was observed in the stereospecificity of tyrosinase immobilized on a chiral (sorbitol cinnamate) or nonchiral (glycerine cinnamate) support.