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Some years ago, in collaboration with Dr. Barry Hall of the University of Rochester, his group investigated a bacterial enzyme which hydrolysed milk sugar (lactose). It could be forced to undergo evolutionary changes. A major question in evolution is "are evolutionary changes dictated by the limited possibilities of the original organism, or by various structures of the outside world". In this case - the ebg system of Eschericia coli - it turned out that the repertoire of amino-acid changes was limited, but that the energetics of the catalysed reaction were all over the place. Consequently in this case the nature of an individual evolutionary change was dictated by the possibilities inherent in the ancestral gene.
Paper from the period 1840-1990 can be very friable, have little fold resistance and indeed in the worst cases can completely disintegrate. The culprit is "rosin-alum" sizing, widespread by 1840, and the received idea in the paper world is that the key process is a proton-catalysed hydrolysis of the cellulose molecules, the protons arising from the hydration-sphere of the Al(III) ion, and the acid pH (~4) of the paper mill water system needed to keep the aluminium in solution. In fact simple mechanistic experiments by Prof Sinnott's group on a model compound, 1,5-anhydrocellobiitol, recently showed that the acid-catalysed hydrolysis route was too slow at pH4 to account for observed rates of deterioration, and that the real culprit was Al(III) acting directly as a electrophile. The decrease of avidity of Al(III)with increase in pH makes it an exaggeration to say that the wholesale deacidification procedures currently being conducted, such as that of the entire archive of the US Library of Congress, are a waste of time, but paper conservators would be better employed tackling the problem at source.
Current projects, largely in collaboration with a group of enzymologists in St. Petersburg, include dteremination of transition state structure of an inulinase y multiple kinetic isotope effects, and measurement of the thermodynamics of glycoside hydrolysis. Equilibrium constants for glycoside hydrolysis are around 100M, so despite a century's investigation of the kinetics of glycoside hydrolysis, their thermodynamics have hitherto proved difficult to measure because of the small proportion of disaccharide present at equilibrium.
Borisova, A., Reddy, S., Ivanen, D., Bobrov, K., Eneyskaya, E., Rychkov, G., Sandgren, M., St�lbrand, H., Sinnott, M., Kulminskaya, A. and Shabalin, K. (2015) ‘The method of integrated kinetics and its applicability to the exo-glycosidase-catalyzed hydrolyses of p-nitrophenyl glycosides’ Carbohydrate Research , 412, pp. 43-49. ISSN 00086215
Borisova, A., Ivanen, D., Bobrov, K., Eneyskaya, E., Rychkov, G., Sandgren, M., Kulminskaya, A., Sinnott, M. and Shabalin1, K. (2015) ‘?-Galactobiosyl units: thermodynamics and kinetics of their formation by transglycosylations catalysed by the GH36 ?-galactosidase from Thermotoga maritima’ Carbohydrate Research , 401, pp. 115-121. ISSN 00086215
Sinnott, M (2007) Carbohydrate chemistry and biochemistry: structure and mechanism . London, UK: Royal Society of Chemistry. ISBN 0854042563
Neustroev, K., Golubev, A., Sinnott, M., Borriss, R., Krah, M., Brumer III, H., Eneyskaya, E., Shishlyannikov, S., Shabalin1, K., Peshechonov, V., Korolev, V. and Kulminskaya, A. (2006) ‘Transferase and hydrolytic activities of the laminarinase from rhodothermus marinus and its M133A, M133C, and M133W mutants’ Glycoconjugate Journal , 23 (7/8), pp. 501-511. ISSN 0282-0080
Brumer, H., Rutland, M., Sinnott, M., Tellervo, T. and Zhou, Q.(2006) Cross-linking involving a polymeric carbohydrate material. WO2006079512.
Baty, J. and Sinnott, M. (2005) ‘The kinetics of the spontaneous proton- and Al(III)-catalysed hydrolysis of 1,5-anhydrocellobiitol models for cellulose depolymerisation in paper aging and alkaline pulping, and a benchmark for cellulase efficiency.’ Canadian Journal of Chemistry , 83, pp. 1516-1524. ISSN 0008-4042
Baty, J. and Sinnott, M. (2004) ‘Efficient electrophilic catalysis of 1,5-anhydrocellobiitol hydrolysis by Al(III); implications for the conservation of rosin-alum sized paper’ Chemical Communications , pp. 866-867. ISSN 1364-548X
Baty, J. and Sinnott, M. (2004) ‘Efficient electrophilic catalysis of 1,5-anhydrocellobiitol hydrolysis by AlIII; implications for the conservation of rosin-alum sized paper’ Chemical Communications (7), pp. 866-867. ISSN 13597345
Von Ossowski, I., Stahlberg, J., Koivula, A., Piens, K., Becker, D., Boer, H., Harle, R., Harris, M., Divine, C., Mahdi, S., Zhao, Y., Driguez, H., Claeyssens, M., Sinnott, M. and Teeri, T. (2003) ‘Engineering the Exo-loop of Cellobiohydrolase, Cel7A. A comparison with Cel7D’ Journal of Molecular Biology , 333 (4), pp. 817-829. ISSN 00222836
Koivula, A., Ruohonen, L., Wohlfahrt, G., Reinekainen, T., Teeri, T., Piens, K., Claeyssens, M., Weber, M., Vasella, A., Becker, D., Sinnott, M., Zou, J., Kleywegt, G., Szardenings, M., Stahlberg, J. and Jones, T. (2002) ‘The active site of cellobiohydralase Ce16A from Trichorderma reesei: the roles of aspartic acids D221 and D175’ Journal of the American Chemical Society , 124 (34), pp. 10015-10024. ISSN 0002-7863
Becker, D., Braet, C., Brumer, H., Claeyssens, M., Divine, C., Fagerstroms, B., Harris, M., Jones, T., Kleywegt, G., Koivula, A., Mahdi, S., Piens, K., Sinnott, M., Stahlberg, J., Teeri, T., Underwood, M. and Wohlfahrt, G. (2001) ‘Engineering of a glycosidase family 7 cellobiohydrolase to more alkaline pH optimum: the pH behaviour of Trichoderma reeseis Ce17A and its E223S/A224/L225V/T226A/D262G mutant’ Biochemical Journal , 356, pp. 19-30. ISSN 0264-6021
The high information-density of structures in which various sugars are connected to each other by glycosidic linkages - two glucoses can be attached as a disaccharide in 40 different ways - makes oligosaccharides the key conveyors of transient information in biological systems, particularly when in turn attached to proteins and lipids. Chemical synthesis of these structures, for medical purposes (e.g. raising antibodies) or biotechnological purposes, is complicated, difficult, and expensive. Enzymic approaches have been used, but use of the enzymes which make the linkages in Nature is restricted by the complexity and cost of the natural glycosyl donors. Therefore the catalytic power of the enzymes which in Nature hydrolyse the link (glycosidases) have been recruited. Two of these methods simple thermodynamic reversal of glycoside hydrolysis, and interception of glycosyl-enzyme intermediates by acceptors requires knowledge glycoside hydrolysis thermodynamics, that is to say the position of equilibrium and the heat (enthalpy) of hydrolysis.
Despite over a century of investigations into the kinetics of glycoside hydrolysis - the kinetics of hydrolysis of sucrose were vital to the formulation of both the Broensted theory of acids and bases and the Michaelis-Menten equation - reported equilibrium constants for disaccharide hydrolysis are sparse, and mostly unreliable. The reason, of course, is that known equilibrium constants are very high (~100M), meaning that solutions 10-30% (w/v) in sugar will have only ~1% of that sugar as disaccharide. Moreover, known glycosidases maintain equilibrium with all possible regioisomers of the disaccharide. Very powerful analytical techniques, such as HPAEC-PAD (high performance anion exchange chromatography with pulsed amperometric detection), which we possess, are therefore needed. Hydrolysis-enthalpies, obtained on single disaccharides will be measured in thecalorimeters of the Huddersfield Thermal Centre.
Ongoing collaboration with the Molecular Biophysics group of the St. Petersburg Nuclear Physics Institute will provide us with the enzymes to establish the appropriate equilibrium.