BCH 380 1st Edition Lecture 19 Outline of Last Lecture II. Coenzymes a. Cofactors b. VitaminsOutline of Current Lecture II. FMN and FADIII. Vitaminsa. Water solubleb. Fat solubleCurrent LectureFAD and FMN- Riboflavin and its coenzymes, FMN and FAD- FMN and FAD participate in oxidation-reduction reactions- They are generally present on the enzyme as prosthetic groupsReduction and reoxidation of FMN or FAD- The conjugated double bonds between N-1 and N-5 are reduced by addition of a hydrideion and a proton to form FMNH2 or FADH2 respectively, the hydroquinone form of each coenzyme- Oxidation occurs in two steps- A single electron is removed by a one-electron oxidizing agentCoenzyme A and Acyl carrier protein (ACP)- These are cosubstrates derived form the vitamin pantothenate, which functions in the transfer of acyl groups Water Soluble:- Thiamine (vitamin B1)- Thiamine diphosphate (TDP)o The thiazolium ring of the coenzyme contains the reactive centero TDP is utilized in carboxylations and decarboxylationsLipoamide- The protein bound form of Lipoic acid- The linkage is via an amide linkage to the E-amino group of a lysine residue in dihydrolipoamide acyltransferases- The reactive center of the coenzyme can be seen in red* Safer to take water soluble vitamins than fat soluble vitamins Vitamin A- A fat soluble vitamin- From Beta-caroteneVitamin E (a reducing agent) and Vitamin K (blood coagulation)- Two more fat soluble vitamins Ubiquinone- Is reduced in two one-electron steps via a semiquinone free-radical intermediate- The reactive center of ubiquinone is shown in red- Also known as coenzyme Q- Q is a stronger oxidizing agent than NAD+Protein Coenzymes- Proteins such as the cytochromes contain Heme groups that allow them to participate inelectron transport- There are three types of cytochromes: cytochrome a, cytochrome b, and cytochrome c- The heme groups of the cytochrome proteins chare a highly conjugated porphyrin ring system, but the substituents of the ring