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Proteins tend to form inactive aggregates at high tempera-tures. We show that polyamines, which have a relatively simple structure as oligoamids, effectively prevent thermal inactivation and aggregation of hen egg lysozyme. In the presence of additives, including arginine and guanidine (100 mM), more than 30% of 0.2 mgÆmL )1 lysozyme in sodium phosphate buffer (pH 6.5) formed insoluble aggre-gates by heat treatment (98 C for 30 min). 1 | Eur. J. Biochem. 270 4547-4554 2003 FEBS 2003 doi 10.1046 j.1432-1033.2003.03850.x Prevention of thermal inactivation and aggregation of lysozyme by polyamines Motonori Kudou1 Kentaro Shiraki1 Shinsuke Fujiwara2 Tadayuki Imanaka3 and Masahiro Takagi1 1 School of Materials Science Japan Advanced Institute of Science and Technology Ishikawa Japan department of Bioscience School of Science and Technology Kwansei Gakuin University Hyogo Japan 3Department of Synthetic Chemistry and Biological Chemistry Graduate School of Engineering Kyoto University Kyoto Japan Proteins tend to form inactive aggregates at high temperatures. We show that polyamines which have a relatively simple structure as oligoamids effectively prevent thermal inactivation and aggregation of hen egg lysozyme. In the presence of additives including arginine and guanidine 100 mM more than 30 of 0.2 mg-mL-1 lysozyme in sodium phosphate buffer pH 6.5 formed insoluble aggregates by heat treatment 98 C for 30 min . However in the presence of 50 mM spermine or spermidine no aggregates were observed after the same heat treatment. The residual activity of lysozyme after this heat treatment was very low 5 even in the presence of 100 mM arginine and guanidine while it was maintained at w 50 in the presence of 100 mM spermine and spermidine. These results imply that polyamines are new candidates as molecular additives for preventing the thermal aggregation and inactivation of heat-labile proteins. Keywords protein misfolding protein aggregation polyamine thermal inactivation. Proteins fold into their unique native structure even in vitro. However they tend to form undesirable and uncontrollable aggregates during the unfolding and refolding processes both in the laboratory and even in their natural environment in living cells. Protein aggregation is a major problem in the large-scale production of recombinant proteins 1-3 as well as in living cells where it may lead to the occurrence of fatal diseases 4 5 . .
