A stepwise regression method was used to search the dipeptides responsible for the optimum temperature (T-opt) of alcohol dehydrogenase, for dipeptides can provide position information of the related residues for rational protein mutation. It was found that the positive dipeptides were RA, GP, GE and LP whereas the negative dipeptides were DD, HQ, PC, QV, YN, DP, QQ, RI, NA and GN. The calculated temperature fitted the experimental optimum temperature of the alcohol dehydrogenase very well and the mean absolute error was only 4.33 degrees C. Using the known crystal structure of alcohol dehydrogenase, we found that most of the positive dipeptides were located in the alpha-helix, while the negative ones were in the beta-sheet, turn or the coil. The thermostable mechanism was discussed and the result obtained could be helpful to engineer alcohol dehydrogenase with high temperature activity. (c) 2006 Elsevier Inc. All rights reserved.