VITAMIN

VITAMINSTRUKTUR, FUNGSI DAN MEKANISMENYA

D

B1

K

E

A

CB3B

2B6B1

2

Merupakan senyawa organik Merupakan komponen dari bahan

pakan Terdapat dalam jumlah kecil Esensial untuk pertumbuhan normal

suatu jaringan, kesehatan, pertumbuhan dan pemeliharaan

Jika kekurangan menyebabkan gejala-gejala spesifik

Beberapa pada ternak tertentu disintesa oleh tubuh (sebagian besar tidak disintesa dalam tubuh)

lanjutan

Digolongkan berdasarkan kesamaan fungsi umum dalam metabolisme

Umumnya terdapat di alam, dapat juga disintesa

Mempunyai ketahanan yang berbeda terhadap cahaya, oksigen, asam, basa dan panas

Ketahanan vitamin terhadap berbagai pengaruh

Pengaruh Vitamin yang peka

Vitamin yang stabil

Cahaya Vit. A, Karoten, Vit.B1, B2, B6, Vit. C, Vit. D, dan Vit E

Choline, as. Pantotenat

Oksigen Vit. A, Karoten, Biotin, Vit.C dan Vit. K

Gol. Vit. Bkomplek, as.nicotinat, Vit.D dan Vit. E

Basa Vit.B1, B2,as. Pantotenat, Vit.C,Vit. E dan Vit.K

Vit. A, Karoten, Vit.B6, Choline, Biotin, Vit.D

Ketahanan vitamin terhadap berbagai pengaruh (lanjutan)

Pengaruh Vitamin yang peka

Vitamin yang stabil

Asam Vit.A, Karoten, Vit.B2, as.pantotenant, Vit.D

Vit. B1,B2,B12, Biotin, Vit.C, Vit.E, dan Vit. K

Panas Vit.A, Vit. B1,B2, Vit. C dan Vit. D

Karoten, Choline, Biotin, Vit. E dan K

KLASIFIKASI VITAMIN Vitamin larut dalam lemak : A, D, E, K Vitamin larut dalam air:

B1 = tiaminB2 = riboflavinAsam pantotenatNiasin = NiacinamideBiotinFolacinB6 = Pyridoxine, Pyridoxal, PyridoxaminB12=Cyanocobalamin, Hydoxocobalamin, AquocobalaminCholineVitamin C = Ascorbic acid, L-ascorbic acid

Perbedaan Vitamin larut dalam lemak dan vitamin larut dalam air

Vitamin larut dalam lemak

Vitamin larut dalam air

Komposisi kimia C,H,O C,H,O + N,S,Co

Terjadinya Jaringan tanaman, ada bentuk provitamin

Pada tanaman, tidak ada bentuk provitamin

Peran fisiologis Kontrol metabolis Transfer energi

Absorbsi lemak air




Penyimpanan Dideposit dalam lemak

Di seluruh sel hidup

Ekskresi Melalui feses Terutama melalui urine.Kadang-kadang ada dalam feses karena ada sintesis oleh mikroba.




Sifat Aktivitas A,D,K= IndividualE=Broad spectrum

Broad spectrum

Kelainan HypovitaminosisHypervitaminosis

Hypovitaminosis

VITAMIN ALAMI

Dalam bahan pakan jumlahnya sangat bervariasi dan tidak ada satu bahan pakan yang mengandung jumlah optimal untuk hewan.

Semua vitamin dibuat di tanaman dan diperoleh hewan apabila mengkonsumsi tanaman

Hewan mengandung mikroorganisme yang sanggup

mensintesis vitamin larut dalam air, provitamin A dan menaquinone (Vitamin K2)

Vitamin B12 hanya bisa disintesis oleh mikro-organisme tertentu tidak bisa oleh tanaman

ataupun hewan

KESTABILAN VITAMIN

Kestabilan vitamin dipengaruhi juga oleh adanya antivitamin seperti : # Avidin yang ada pada putih telur akan mengikat biotin # Thiaminase pada ikan menghambat tiamin # l-amino-D-prolin pada flaxseed membentuk komplek stabil dengan pyridoxine

GENERAL VITAMIN STABILITY

VITAMIN STABILITY CHARACTERISTIC

A Oxidasi khususnya dengan Fe,Cu

D3 Oxidasi (kestabilan sedang)

E Stabil dalam bentuk acetat, sangat

tidak stabildalam bentuk alcohol

K Sangat tidak stabil

Tiamin Sensitif terhadap oxidasi dan pH

GENERAL VITAMIN STABILITY VITAMIN STABILITY CHARACTERISTIC

Pyridoksin, Kestabilan sedang

riboflavin

Pantotenat Sensitif hidrolisis

Niasin Hampirstabil

B12 Kestabilan tinggi, beberapa hilang bila kedaluwarsa

Biotin Hampir stabil

Asamfolat Kestabilan sedang, sensitif oxidasi dan reduksi

Vitamin C Sangat tidak stabil dalam bentuk

alami

VITAMIN LARUT DALAM LEMAK

Vitamin A (Retinol)R=CH2OH Retinol

R=CH2OH Retinal

R=CH2OH Asam Retinoat

Vitamin A (Retinol)

CH3

CH3H3COH

CH3CH3

Retinol

b - Carotene and Retinol

CH3

CH3

CH3 CH3 CH3

CH3 CH3 CH3

H3 C

CH3

H3 C CH3

CH3

CH3 CH3

H3 C CH3

CH3

CH3 CH3

CH2 OH

Oxidation

C H

O

Retainal

Retinol (Vitamin A)

- 2H

Fungsi Vitamin A

1.Rangsangan cahaya dari mata ke otak

2.Berperan dalam sel epitel

3.Mengontrol aktivitas tulang

The vision cycleOpsin balok : rodopsinOpsin kerucut : iodopsin

Defisiensi Vitamin A

1.Buta malam

2.Seroptalamia (pengeringan & iritasi kornea, keruh dan mudah terinfeksi)

3.Terganggu sel

Vitamin D D2=Ergokalsiferol

D3=Kholekalsiferol

Pro Vit D2 = ergosterolPro Vit D3 = 7 dehidrokholesterol

Fungsi Vitamin D 1. Proses absorpsi2. Proses reabsorpsi3. Deposisi

Defisiensi Vitamin D

1. Rakhitis2. Osteomalasia

Vitamin E Vit E bentuk jenuhAlfatokoferol, Betatokoferol, Gamatokoferol, Deltatokoferol

Vit E bentuk tidak jenuhAlfatokotrienol, Betatokotrienol, Gamatokotrienol, Deltatokotrienol

Fungsi Vitamin E1. Reproduksi

2. Generasi

3. Hati dan Metabolisme

4. Memperbaiki absorpsi Fe

5. Antioksidan

Defisiensi Vitamin E

1. Kemunduran Reproduksi2. Gangguan permeabilitas3. Kerusakan otot

Vitamin K K1 = FiloquinonK2 = MenaquinonK3 = Menadion

Fungsi Vitamin KKoagulasi darah dengan mengaktifkan prothrombin (sintesis prothrombin didalam hati)

Thrombin Activation

co llagen

WO UNDv W F

endo th eliu m

p la te le tPL surfa c e

C a

C a

Va

Xa

C ircu la tio n

N H2C O O H

G la G la

P ro -T h ro m b in

SS

p ro teo ly tic cu t

N H2C O O H

G la G la

T h ro m b inP ro -

SS

Fibrinogen + thrombin------------- Fibrin + Peptida

Defisiensi Vitamin K

1. Pembekuan darah terganggu

FUNGSI BIOKEMIS VITAMIN Vitamin Fungsi Biokemis

A -Essensial u/ pembentukan rhodopsin (melihat dlm gelap), pada reproduksi tikus,u/memelihara plasenta ½ periode kebuntingan yang kedua, Sintesa mukopolisakarida dan proses pembentukan tulang

D -Mempengaruhi metabolisme Ca dan P (memperbaiki ossifikasi dan deposisi dalam kartilago dan kulit telur) serta menaikkan aktivitas enzim phytase pd usus tikus

E antioksidan,berperan pada pernafasan jaringan,fosforilsasi dari kreatin fosfat, sintesa as.askorbat dan metabolisme a.a yg mgd belerang

K Proses pembekuan darah (sintesa prothrombin & bbrp protein plasma), pembentukan RNA

VITAMIN LARUT DALAM AIR

33

Vitamins in Metabolic Pathways

Glycolysis

TCAcycle

Glycogenolysis

aKGDHvit B1,B2,B3

PP avit B6

Glc

GlycogenG1P

R5PTK

vit B1

PDHvit B1,B2,B3

aKGSCoA

Acetyl-CoA

G6P

Pyr

G3PALT

vit B6

Ala

ASTvit B6

OAAsp

vit B6 Glu

PPP

Vitamin B1

Thiamine pyrophosphate (TPP) Thiamine - a thiazole ring joined to a

substituted pyrimidine by a methylene bridge

Thiamine-PP is the active form TPP is involved in carbohydrate

metabolism It catalyzes decarboxylations of alpha-

keto acids and the formation and cleavage of alpha-hydroxyketones

Thiamine PyrophosphateReactions and rationale

Yeast pyruvate decarboxylase, acetolactate synthase, transketolase, phosphoketolase

All these reactions depend on accumulation of negative charge on the carbonyl

carbon at which cleavage occurs! Thiamine pyrophosphate facilitates these

reactions by stabilizing this negative charge The key is the quaternary nitrogen of the

thiazolium group

Riboflavin and the Flavins

Vitamin B2 All these substances contain ribitol and a

flavin or isoalloxazine ring Active forms are flavin mononucleotide

(FMN) and flavin adenine dinucleotide (FAD)

FMN is not a true nucleotide FAD is not a dinucleotide But the names are traditional and they

persist!

Flavin Mechanisms

Flavins are one- or two-electron transfer agents

Name "flavin" comes from Latin flavius for "yellow"

The oxidized form is yellow, semiquinones are blue or red and the reduced form is colorless

Study the electron and proton transfers in Figure 18.22

Other transfers are possible!

Coenzyme APantothenic acid (vitamin B3) is a

component of Coenzyme A Functions:

Activation of acyl groups for transfer by nucleophilic attack

activation of the alpha-hydrogen of the acyl group for abstraction as a proton

Both these functions are mediated by the reactive -SH group on CoA, which forms thioesters

Nicotinic Acid and the Nicotinamide Coenzymes

aka pyridine nucleotides These coenzymes are two-electron

carriers They transfer hydride anion (H-) to and

from substrates Two important coenzymes in this class:

Nicotinamide adenine dinucleotide (NAD+)

Nicotinamide adenine dinucleotide phosphate (NADP+)

Nicotinamide Coenzymes

Structural and mechanistic features The quaternary nitrogen of the

nicotinamide ring acts as an electron sink to facilitate hydride transfer

The site (on the nicotinamide ring) of hydride transfer is a pro-chiral center!

Hydride transfer is always stereospecific!

Be sure you understand the pro-R, pro-S designations

Last Notes on Nicotinamides

Nicotinamide was first isolated in 1937 by Elvehjem at the University of Wisconsin

Note similarities between structures of nicotinic acid, nicotinamide and nicotine

To avoid confusion of names (and functions!), the name niacin (for nicotinic acid vitamin) was suggested by Cowgill at Yale.

Biotin

"Chemistry on a tether" Biotin functions as a mobile carboxyl

group carrier Bound covalently to a lysine The biotin-lysine conjugate is called

biocytin The biotin ring system is thus

tethered to the protein by a long, flexible chain

Biotin Carboxylations

Most use bicarbonate and ATP Whenever you see a carboxylation that

requires ATP and CO2 or HCO3-, think

biotin! Activation by ATP involves formation of

carbonyl phosphate (aka carboxyl phosphate)

Carboxyl group is transferred to biotin to form N-carboxy-biotin

The "tether" allows the carboxyl group to be shuttled from the carboxylase subunit to the transcarboxylase subunit of ACC-carboxylase

Folic Acid

Folates are donors of 1-C units for all oxidation levels of carbon except that

of CO2 Active form is tetrahydrofolate (THF) THF is formed by two successive

reductions of folate by dihydrofolate reductase

Know how to calculate oxidation states of C!

Vitamin B6

Pyridoxine and pyridoxal phosphate Catalyzes reactions involving amino

acids Transaminations, decarboxylations,

eliminations, racemizations and aldol reactions

See Figure 18.26 This versatile chemistry is due to:

formation of stable Schiff base adducts

a conjugated electron sink system that stabilizes reaction intermediates

Pyridoxal Phosphate

Mechanisms Figure 18.27 is a key figure - relate

each intermediate to subsequent mechanisms

Appreciate the fundamental difference between intermediates 2-5 and 6,7

Vitamin B12

Cyanocobalamin

B12 is converted into two coenzymes in the body: 5'-deoxyadenosylcobalamin

methylcobalamin

Vitamin B12

Cyanocobalamin

Dorothy Hodgkin determined the crystal structure of B12 in 1961 - at the time it was the most complicated structure ever elucidated by X-ray diffraction and she won a Nobel prize

Most striking feature - the C-Co bond length of 0.205 nm (2.05 A) - an essentially covalent bond

B12 Function & Mechanism

See Figures 18.28-18.29 B12 catalyzes 3 kinds of reactions:

Intramolecular rearrangements

Reductions of ribonucleotides to deoxyribonucleotides

Methyl group transfers (assisted by tetrahydrofolate )


B1 (Tiamin) -Koenzim pd proses dekarboksilasi ketoacid (Co : as. Piruvat)

B2 (Riboflavin) -Dlm bntk flavin mononucleatid (FMN) dan flavin adenin dincleatid (FAD) bertindak sbg gugus prostetik dari bbrp enzim dlm r. oksidasi-reduksi dlm tubuh

B6 (Pyridoxine) Koenzim proses dekarboksilasi,deaminasi dari serine dan threonine, transaminasi, transulfrasi, & transfer a.a. dalam sel

Nicotinaminde(Niasin)

-komponen koenzim NAD dan NADP dalam transport hidrogen


As. Panthotenat -Merupakan gugus prostetik koenzim A yg mpy fungsi dlm r. acetilasi pada KH, lemak dan metabolisme a.a.

Vit. B12 -Koenzim sintesa as. Nukleat (RNA), pembentukan gugus methyl pada thyamine

Choline Pembentukan dan pemeliharaan sel-sel tubuh, sbg methyldonator

Vit. C Pembentukan kolagen,dibutuhkan dlm perb. As.folat mjd tetra hydrofolic acid, proses hydroxylasi prolin,lysine & anilin / fungsi normal fisiologis.

GEJALA DEFISIENSI VITAMINVITAMIN GEJALA DEFISIENSI

A Keratinisasi Xeropthalmia

D Ricket Osteomalacia

E Muscular distropy Exudativediathesis Encephalomalcia

K Terhambatnyaproses pembekuan darah

GEJALA DEFISIENSI VITAMIN

VITAMIN GEJALA DEFISIENSI

Tiamin (B1) Anorexsia, polineuritis, nafsu mkn turun

Riboflavin Curled toe paralysis, nafsu mkn turun,diare

As.pantotenat Pertumbuhan badan & bulu terhenti, Dermatitis (pelupuk mata,sudut mulut,kaki),goose step(babi)

Niasin Pellagra (dermatitis, diare, dementia), anemianafsu mkn turun,pertumbuhan terganggu

Pyridoksin Convulsi (kekejangan), anemia, nafsu mkn turun

Biotin Perosis, dermatitis

Asam folat Anemia, pertumbuhan terhambat, bulu jelek, depigmentasi, perosis

Kholin Hati berlemak, perosis (babi),gangguan pertumbuhan & pembtk kuning telur

Cobalamin Pertumbuhan yg tidak baik,Anemia, kegagalan fungsi reproduksi

KERACUNAN VITAMINVitamin Safe Upper Feed Safe Upper

Level(unit/kg Level+ Normal

pakan) Level

A 80.000 IU/kg 10

D3 10.000 IU/kg >60 d 3-4

50.000 IU/kg < 20 d 20-30

E 1000 IU/kg 20-30

K 2000 mg/kg 1000

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VITAMIN