The diffusive transport and mixing times of regulatory molecules in micrometer and submicrometer_ reaction volumes can be shorter than characteristic times of conformational transformations in single enzyme molecules. Under these conditions, mutual synchronization of individual molecular turnover cycles takes place when strong allosteric activation by the reaction products is present. Using simple automaton models to describe the cycles of single molecules, we analyze properties of the synchronization transition and the role of statistical fluctuations in the synchronization phenomena.