A method for rapidly and highly sensitively measuring endotoxin relies on an endotoxin-measuring agent, which includes a factor C derived from Tachypleus tridentatus that does not have His-tag sequence at the C-terminus, a factor B of a horseshoe crab, and a proclotting enzyme of a horseshoe crab. Each of these proteins can be a recombinant protein obtainable by being expressed using a stably expressing cell line of an insect cell as a host.

A method for rapidly and highly sensitively measuring endotoxin relies on an endotoxin-measuring agent, which includes a factor C derived from Tachypleus tridentatus that does not have His-tag sequence at the C-terminus, a factor B of a horseshoe crab, and a proclotting enzyme of a horseshoe crab. Each of these proteins can be a recombinant protein obtainable by being expressed using a stably expressing cell line of an insect cell as a host.

A method for rapidly and highly sensitively measuring endotoxin relies on an endotoxin-measuring agent, which includes a factor C derived from Tachypleus tridentatus that does not have His-tag sequence at the C-terminus, a factor B of a horseshoe crab, and a proclotting enzyme of a horseshoe crab. Each of these proteins can be a recombinant protein obtainable by being expressed using a stably expressing cell line of an insect cell as a host:

A reagent for -glucan measurement without requiring a horseshoe crab hemocyte extract by using horseshoe crab-derived factor D in the reagent for -glucan measurement.

A method for rapidly and highly sensitively measuring endotoxin is provided. Endotoxin is measured using an endotoxin-measuring agent comprising the proteins (1) to (3) below, each of which is a recombinant protein obtainable by being expressed using insect cells as a host: (1) a factor C derived from Tachypleus tridentatus, which factor C does not have a His-tag sequence at the C-terminus; (2) a factor B of a horseshoe crab; and (3) a proclotting enzyme of a horseshoe crab.