cofactor

noun

1. 1.A contributing factor.
2. 2.A substance, especially a coenzyme or a metal, that must be present for an enzyme to function.
3. 3.A molecule that binds to and regulates the activity of a protein.
4. 4.The result of a number being divided by one of its factors.
5. 5.(of a matrix) The signed determinant of the submatrix produced by removing the row and column containing a specified element; primarily used in the recursive definition and calculation of the determinant of a matrix.