Kyoto University Press, Kyoto. Bonner, W. A. (1991). The Origin and amplification of biomolecular chirality. Origins of Life and Evolution of Biosphere, 21:59–111. Munegumi, T. and Shimoyama, A (2003). Development of homochiral peptides in the chemical evolutionary process: separation of homochiral and heterochiral oligopeptides. Chirality,15: S108-S115. Munegumi, T., Takayama, N., Ebina, T. and Sawahata, M. (2005). Stereo-specific condensation of activated amino acids or peptides. Viva Origino, 33:151–151. Plasson, R., Kondepudi, D. K., Bersini, H., Commerras, A., and Asakura, K. (2007). Emergence of homochirality in far-from-equilibrium systems: mechanisms and role in prebiotic

chemistry. Chirality, 19: 589–600. E-mail: munegumi@oyama-ct.​ac.​jp Small EPZ015666 structural Change Producing Tryptophanase Activity on D-tryptophan Akihiko Shimada Sustainable Environmental SB525334 Studies, Graduate School of Life and Environmental Sciences, University

of Tsukuba, Tsukuba, Japan Tryptophanase (TPase) is an enzyme with extremely tight stereospecificity, cleaving l -tryptophan into indole, having no activity on D-tryptophan under ordinary conditions. However, it becomes active toward d-tryptophan in highly concentrated ammonium phosphate solutions quite different from what was expected. The only salts inducing the reaction were diammonium NVP-HSP990 supplier phosphate, triammonium phosphate and ammonium sulfate, although other salts didn’t have the activity at all. Free tryptophan is more readily influenced by alkaline pH or strong ion strengths than other biological amino acids. If ammonium phosphates affect chemical racemization on D-tryptophan, the enzymological significance of this reaction is lost. So it is important to demonstrate that ammonium phosphates do not racemize free D-tryptophan at all. We used an HPLC column appropriate for tryptophan resolution to analyze free D-tryptophan, demonstrating that the reaction is enzymatic metabolism (Shimada, 2007). Ammonium phosphates as diammonium hydrogenphosphate or triammonium phosphate probably produce

structural change in tryptophanase, which makes it possible that activity on D-tryptophan will emerge. This result indicates enzyme stereospecificity Idoxuridine is more flexible than we think. Judging from the flexibility of tryptophanase stereospecificity, this conformational change is maybe small. Circular dichroism analyses were thus applied to tryptophanase in ammonium phosphate solution. A 200 μL of monoammonium hydrogenphosphate (MAP), diammonium hydrogenphosphate (DAP), and triammonium phosphate (TAP) of 50% saturation and phosphate buffer (PB) solutions with 0.5 μM of apoTPase and 1.1 mM of PLP was injected in a 0.1 cm path length cell in a circular dichroism (CD) spectrophotometer. Spectra were recorded at wavelengths from 200 to 350 nm at room temperature. Five scans were repeated per a spectrum, averaged, and expressed as molar ellipticity in degrees cm2 dmol -1.

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