Involved in galactose catabolism. Catalyzes the phosphorylation of 2-keto-3-deoxygalactonate (KDGal) to produce 2-keto-3-deoxy-6-phosphogalactonate (KDPGal). Can also phosphorylate 2-keto-3-deoxygluconate (KDG) to 2-keto-3-deoxy-6-phosphogluconate (KDPG), but the catalytic efficiency for KDGal is 50-fold higher than for KDG. 2-dehydro-3-deoxy-D-galactonate + ATP = 2-dehydro-3-deoxy-6-phospho-D-galactonate + ADP + H(+) Homohexamer. Highly induced by galactose. Deletion of the gene does not affect growth on glucose or galactose. Double deletion mutant kdgK1/kdgK2 loses the ability to grow on galactose. Belongs to the carbohydrate kinase PfkB family.