Positive regulator of gsk3/gskA activity required for cell pattern formation and a downstream effector of carC. The kinases, gsk3/gskA, zakA and zak2, form part of a signaling pathway that responds to extracellular cyclic AMP. The pathway has a role in transcriptional regulation; required to direct prespore/spore fates during development. ZakA negatively regulates prestalk differentiation by regulating expression of ecmB. Phosphorylates Y-214 of gsk3/gskA, in vitro. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] ATP + L-tyrosyl-[protein] = ADP + H(+) + O-phospho-L-tyrosyl-[protein] ZakA and zak2 are coexpressed in prestalk cell population, zakA is enriched in pstB populations and zak1 in pstA populations. ZakA and zak2 are coexpressed in prespore cells, zakA expression levels are 10 fold higher than zak2. Expression is first seen at 5 hours of development during aggregation, reaching peak expression at slug stage (15 hours). N-terminal serine/threonine domain is capable of autophosphorylation, in vitro, but to a lower extent than the tyrosine kinase domain. May function as a negative regulator of the tyrosine kinase domain. C-terminal tyrosine kinase domain is capable of autophosphorylation, in vitro. 'Zaphod' is a fictional ex-president of the galaxy with 2 heads. In the N-terminal section; belongs to the protein kinase superfamily. Ser/Thr protein kinase family. In the C-terminal section; belongs to the protein kinase superfamily. TKL Tyr protein kinase family.