Serine/threonine-protein kinase that plays a role in many biological processes such as fatty acid oxidation, autophagy, immune response or glucose metabolism (PubMed:23322770, PubMed:26983400). Phosphorylates 'Ser-794' of IRS1 in insulin-stimulated adipocytes, potentially modulating the efficiency of insulin signal transduction. Inhibits CREB activity by phosphorylating and repressing TORCs, the CREB-specific coactivators (PubMed:15454081). Phosphorylates EP300 and thus inhibits its histone acetyltransferase activity (PubMed:21084751, PubMed:26983400). In turn, regulates the DNA-binding ability of several transcription factors such as PPARA or MLXIPL (PubMed:21084751, PubMed:26983400). Also plays a role in thymic T-cell development (By similarity). {ECO:0000250|UniProtKB:Q8CFH6, ECO:0000269|PubMed:15454081, ECO:0000269|PubMed:21084751, ECO:0000269|PubMed:23322770, ECO:0000269|PubMed:26983400}. This is the function of SIK2 (salt inducible kinase 2, Ensembl gene identifier ENSG00000170145).