Dr. Saidunnisa

Associate ProfessorDepartment of Biochemistry

Lecture-Coenzymes

Learning Objectives

• At the end of the session student shall be able to :

• Define and classify coenzymes.• Explain the biochemical role of coenzymes.• Interpret their role in various disorders.

Coenzymes• Some enzymes need assistance from other

molecules (such as vitamins) in order to facilitate the transformation of chemical reactants into products. These other molecules are collectively referred to as coenzymes.

• These are heat stable, low-molecular weight, non protein organic substances function with enzymes in the catalytic processes.

• Coenzymes are second substrates or co-substrates

• Most of them are derivatives of B-complex vitamins.

• The functional enzyme is referred to as holoenzyme which is made up of :

• Protein part (apoenzyme) • Non protein part (coenzyme)

classification

• First group-take part in transfer of hydrogen atoms. (oxidoreductases)

eg:-NAD/NADH+H,NADP/NADPH, FAD/FADH2,FMN/FMNH2• Second group -take part in transferring groups

other than hydrogen. eg: PLP,TPP, Biotin, THF, Cobalamin.

First group

Oxidative decarboxylation (PDH Complex)

First group

• First group

• Niacin• Oxidation-reduction• Pellagra • NAD/NADP

First group

• Riboflavin (B2)

• FMN/FAD• Oxidation-reduction• Chelosis and glositis

Second group

• Pyridoxine (B6)

• Transamination• PLP• Neurological symptoms

Folic acid and B12 Coenzymes

One carbon Isomerism

CoenzymeCoenzyme Derived Derived from from VitaminVitamin

Physiologic Physiologic functionfunction

deficiencydeficiency

TPPTPP Thiamine Thiamine (B(B11))

Oxidative Oxidative decarboxylationdecarboxylation

Dry and Dry and wet beri wet beri beriberi

FMN/FADFMN/FAD Riboflavin Riboflavin (B(B22))

Oxidation-Oxidation-reductionreduction

ChelosisChelosis

NAD/NADPNAD/NADP NiacinNiacin Oxidation-Oxidation-reductionreduction

PellagraPellagra

PLPPLP Pyridoxine Pyridoxine (B(B66))

TransaminationTransamination Neurological Neurological symptomssymptoms

BiotinBiotin BiotinBiotin CarboxylationCarboxylation Alopecia/dry Alopecia/dry skin/dermatitisskin/dermatitis

CoenzymeCoenzyme Derived Derived from from VitaminVitamin

Physiologic Physiologic functionfunction

deficiencydeficiency

Methyl/Methyl/deoxyadenodeoxyadenosyl syl cobalaminecobalamine

BB1212 IsomerismIsomerism Megaloblastic Megaloblastic anemiaanemia

TetrahydrofolTetrahydrofolate (THF)ate (THF)

Folic acidFolic acid One carbon One carbon metabolismmetabolism

Microcytic Microcytic anemiaanemia

Coenzyme ACoenzyme A Pantothenic Pantothenic acidacid

Acyl groupAcyl group Burning feet Burning feet syndromesyndrome

Non-Vitamin coenzymesCoenzyme Abbreviation Biochemical Function

Adenosine triphosphate ATP Donates phosphate

Cytidine diphosphate CDP Required in phospholipid synthesis

Uridine diphosphate UDP Required in glycogen synthesis

S-adenosylmethionine SAM Donates methyl group

Phosphoadenosine phosphosulfate

PAPS Donates phosphate