<prompt> C1 is controlled by?CalciumMagnesiumManganesePhosphate  <response>: The initial enzyme, Cl, is a complex formed through a calcium-dependent association between two reversibly interacting subunits, Clq and Clr2s2.In the absence of an immune response, approximately 70 of Cl exists as a complex between these two subunits.Cl occurs in serum as a proenzyme that tends to undergo autoactivation in which the two subunits are bound together but is strictly controlled by Cl-inhibitor Cl-In or Cl esterase. 