H+ ATPase of the plasma membrane of yeast is a polytopic protein with 1000 amino acids that couples ATP hydrolysis with H+ pumping through the membrane. The electrochemical gradient generated is used to support nutrient and ion transportation. During its catalytic cycle it alternates between two well defined conformations (E1, E2) and a phosphorylated intermediary is formed that contains an aspartyl phosphate residue. Enzyme activity in the cell is regulated at both a transcriptional and post-traductional level in response to the changing conditions of the external medium. Of these, glucose is one of the most important signals in this modulation process since it induces the synthesis of new ATPases, and phosphorylation of the enzyme's carboxyl terminal region , which leads to an increase in activity. Due to the importance of ATPase in cell economy and its relative structural simplicity, it was considered to be a good model for the study of energy transduction phenomena, including the ATP hydrolysis mechanism.
Another protein we are interested in is the deacetylase of E. coli, a tetrameric protein comprising identical subunits of 41 kDa that form part of the amino sugar utilization pathway in E. coli. From the kinetic point of view, it has a sequential mechanism with an ordered release of products and slow isomerization of central complexes. In both senses, inhibition by substrate can be found.