21. Its activation in vivo requires the attachment of a lipoic acid prosthetic group at Lys59 of the mature protein. 22. A coenzyme that is tightly or even covalently bound is termed a "'prosthetic group " '. 23. Other oxygen transporting proteins have a very low dissociation constant with their metal prosthetic group and bind these groups tightly. 24. Organic prosthetic groups can be covalently bound ( e . g ., biotin in enzymes such as pyruvate carboxylase ). 25. Of particular functional importance are the flavin prosthetic group ( FMN ) and eight iron-sulfur clusters ( FeS ). 26. Aequorin is a holoprotein composed of two distinct units, the kDa, and the prosthetic group coelenterazine, the luciferin. 27. A heme is a prosthetic group that consists of an iron atom contained in the center of a heterocyclic porphyrin ring. 28. The human thromboxane A ( TXA ) synthase is a 60 kDa protein with 533 amino acids and a heme prosthetic group . 29. The electrons are then transferred through a series of iron sulfur clusters : the second kind of prosthetic group present in the complex. 30. Flavoproteins have either an FMN or FAD molecule as a prosthetic group , this prosthetic group can be tightly bound or covalently linked.
