Chapter 7 part 1
Download
1 / 22

Chapter 7 part 1 - PowerPoint PPT Presentation


  • 181 Views
  • Uploaded on

Chapter 7 (part 1). Cofactors. Cofactors. Cofactors are organic or inorganic molecules that are required for the activity of a certain conjugated enzymes Apoenzyme = enzyme (-) cofactor Holoenzyme = enzyme (+) cofactor Inorganic cofactors – essential ions Organic cofactors – coenzymes.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Chapter 7 part 1' - letitia


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

Cofactors l.jpg
Cofactors

  • Cofactors are organic or inorganic molecules that are required for the activity of a certain conjugated enzymes

  • Apoenzyme = enzyme (-) cofactor

  • Holoenzyme = enzyme (+) cofactor

  • Inorganic cofactors – essential ions

  • Organic cofactors – coenzymes


Essential ion cofactors l.jpg
Essential Ion Cofactors

  • Activator ions – bind reversibly to enzyme and often participate in substrate binding.

  • Metal ions of metalloenzymes – cations that are tightly bound to enzyme and participate directly in catalysis (Fe, Zn, Cu, Co).

  • Metal activated enzymes – require or are stimulated by addition of metal ions (i.e. Mg2+, is required by many ATP requiring enzymes)


Metal ions can function as electrophiles in active site l.jpg
Metal ions can function as electrophiles in active site

Zinc protease (angiotensin converting enzyme)


Coenzymes l.jpg
Coenzymes

Cosubstrates-

- altered in rxn and regenerated to original structure in subsequent rxn

- disassociated from active site

- shuttle chemical groups among different enzyme rxns.

Prosthetic groups-

- remains bound to enzyme

- must return to original form

Both cosubstrates and prosthetic groups supply reactive groups not present on amino acid side chains


Coenzymes6 l.jpg
Coenzymes

  • Metabolite coenzymes – synthesized from common metabolites

  • Nucleoside triphosphates – (ATP) can donate phosphates, pyrophosphates, adenosyl grroups

  • S-adenosylmethionine (SAM) – donates methyl groups

  • Nucleotide sugars (uridine diphosphate glucose = UDP-glucose) - transfer sugars in carbohydrate metabolism


Vitamin derived coenzymes l.jpg
Vitamin derived coenzymes

  • Must be obtained from diet

  • Synthesized by microorganisms and plants

  • Vitamin deficiencies lead to disease state

  • Most vitamins must be enzymatically transformed to function as a coenzyme


Vitamins l.jpg
Vitamins

VitaminCoenzyme

Ascorbic acid (C) not a coenzyme

Niacin NAD(P)+/NAD(P)H

Riboflavin (B2) FMN & FAD

Thiamin (B1) Thiamin-pyrophosphate

Pyridoxal (B6) Pyridoxal phosphate

Biotin Biotin

Folate Tetrahydrafolate

Cobalamin (B12) adenosyl-and methylcobalamin

Vitamin A Retinal

Vitamin K Vitamin K

Pantothenate (B3) Coenzyme A


Niacin nicotinic acid l.jpg
Niacin (nicotinic acid)

  • Deficiencies lead to pellagra (dermatitis, diarrhea, dementia)

  • Required in relatively high amounts compared to other vitamins

  • Not true enzyme because can be synthesized from tryptophan in the liver



Nad nadp l.jpg
NAD+ / NADP+

  • Serve as cofactors in oxidation/reduction reactions

  • Act as co-substrates for dehydrogenases

  • Reduction of NAD+/NADP+ and oxidation of NADH/NADPH occurs 2 e- at a time.

  • Function in hydride ion transfer

  • Rxns forming NADH/NADPH are catabolic

  • NADH is coupled with ATP production in mitochondria

  • NADPH is an impt reducing agent in biosynthetic reactions

  • Reduced forms (NADH/NADPH) absorb light at 340 nm, oxidized forms (NAD+/NADP+) do not


Riboflavin b2 l.jpg
Riboflavin (B2)

  • Water soluble vitamin

  • Severe deficiencies lead to growth retardation, reproductive problems and neural degeneration

  • Meat, dairy products and dark green vegetables, legumes and grains are good sources



Fad and fmn can transfer electrons one or two at a time l.jpg
FAD and FMN can transfer electrons one or two at a time

Hydroquinone

form

Quinone

form

semiquinone form


Thiamin l.jpg
Thiamin

  • Thiamin is the first Vitamin discovered (Vital amine = Vitamin)

  • Deficiencies lead to disease called Beriberi (neurological disorders, heart problems, anorexia)

  • Beriberi prevealent in undeveloped countries where polished grains make up the majority of the diet.

  • Associated with alcohol related disorders (Wernickes-Korskofff syndrome – memory loss, unstable walk)


Thiamin pyrophosphate l.jpg
Thiamin pyrophosphate

  • Serves as a cofactor in decarboxylation rxn of keto acids

  • Also functions as a prosthetic group in transketolases (catalyze the transfer of two carbon units in carbohydrate metabolism)


Thiazolium ring is the chemically active part of tpp l.jpg
Thiazolium ring is the chemically active part of TPP

Ylid = a molecule with opposite charges on adjacent atoms



Pyridoxal phosphate l.jpg
PYRIDOXAL-PHOSPHATE

  • Important in amino acid metabolism

  • Bound to enzyme as a Schiff base thru rxn with lysine

  • PLP functions in transamination, decarboxylation, racemization, isomerization, side-chain elimination rxns involving amino acids




ad