The key role of glycerate kinase in carbohydrate metabolism. Current knowledge about the physiological function of glycerate kinases of the different glycerate kinase classes in extant living organisms is shown (according to Table 3). The different carbon sources/pathways and organisms are boxed and the color indicates the involvement of glycerate kinases of the three different glycerate kinase classes (class II GK (MOFRL family), white; class I GK, light grey; class III GK, dark grey) in the respective metabolic pathway. The formation of 2- or 3-phosphoglycerate is indicated by the name of the enzyme family indicated below the compounds. The suggested function of the class I and class II (MOFRL family) glycerate kinases in Pseudomonas fluorescens and P. putida is indicated by dashed lines.