The tributyrinase activity of C7.

Several serum fractions containing the seventh component of complement have the capacity of liberating fatty acids from a tributyrin substrate. Reagent H (gp) is depleted of its tributyrinase content after it has reacted with an EAC142 intermediate and so had the possibility of completing the formation of an EAC1–7 intermediate. The enzyme content of reagent H remains unchanged after contact of H with EA cells. EAC1–7 intermediates prepared by five different techniques with various sources of C7, when submitted to Weiner's elution method liberate a tributyrinase. This has never been found in eluates made from intermediates prior to the EAC1–7 stage, that is from EAC1 through EAC1–6. It is concluded that an enzyme shown to have the properties of a tributyrinase is responsible for the activity of haemolytic C7.