In enzymology, an ubiquitin-calmodulin ligase (EC 6.3.2.21) is an enzyme that catalyzes the chemical reaction

n ATP + calmodulin + n ubiquitin ${\displaystyle \rightleftharpoons }$ n AMP + n diphosphate + (ubiquitin)n-calmodulin

The 3 substrates of this enzyme are ATP, calmodulin, and ubiquitin, whereas its 3 products are AMP, diphosphate, and (ubiquitin)n-calmodulin.

This enzyme belongs to the family of ligases, specifically those forming carbon-nitrogen bonds as acid-D-amino-acid ligases (peptide synthases). The systematic name of this enzyme class is calmodulin:ubiquitin ligase (AMP-forming). Other names in common use include ubiquityl-calmodulin synthase, ubiquitin-calmodulin synthetase, ubiquityl-calmodulin synthetase, and uCaM-synthetase.

• Jennissen HP, Laub M (1988). "Ubiquitin-calmodulin conjugating activity from cardiac muscle". Biol. Chem. Hoppe-Seyler. 369 (12): 1325–30. doi:10.1515/bchm3.1988.369.2.1325. PMID 2853950.
• Ziegenhagen R, Jennissen HP (1988). "Multiple ubiquitination of vertebrate calmodulin by reticulocyte lysate and inhibition of calmodulin conjugation by phosphorylase kinase". Biol. Chem. Hoppe-Seyler. 369 (12): 1317–24. doi:10.1515/bchm3.1988.369.2.1317. PMID 2853949.