The celebrants of the sacramental liturgy
In the celebration of the sacraments it is thus the whole assembly that is leitourgos, each according to his function, but in the "unity of the Spirit" who acts in all. "In liturgical celebrations each person, minister or layman, who has an office to perform, should carry out all and only those parts which pertain to his office by the nature of the rite and the norms of the liturgy."
Source: Catechism of the Catholic Church (Vatican.va)