Chapter 9

1. Chapter 9 Protein and Amino Acids

2. Protein vary widely in chemical composition, physical property, size shape, solubility, biological function.

3. General structure of amino acid NH2 O R —— C ——C OH OH • R is the remainder of the molecule attached to the C atom associated with the α-amino group of the amino acid.

4. Amino acids not synthesized in animal tissues of most specie in sufficient amounts to meet are termed essential or indispensable, whereas those generally not needed in the diet because of adequate tissue synthesis are termed nonessential or dispensable.

5. Essential Arginine Histidine Isoleucine Leucine Lysine Methionine Phenylalnine Threonine Tryptophen Valine Nonessential Alanine Aspartic acid Citrulline Cystine Glutamic acid Glycine Hydroxyproline Proline Serine tyrosine

6. Arginine: is required for some species for maximum growth, adult do not require. However dog, cat show severe sign of deficiency. • Glutamine: is a dispensable, 但生病時, 是唯持正常代謝所需，是indispensable.

7. In most animal: • in mucosa : glutamate＋proline合成ornithine ，ornithine轉成citrulline，再送至 腎臟產生arginine( urea cycle) • In cat、 dog: ornithine→citrulline與citrulline→arginine未能進行，∴arginine is essential。在higher protein ，缺arginine 無法進行urea cycle，引起hyperammonia

8. Taurine : • Synthesized by most mammals from methionine and cysteine • It is indispensable for cat only. • a amino sulfonic acid, occurs as a free amino acid. is not present in protein • develop degeneration of retina of the eye.(myocardium and retina contain high concentration of free taurine) • Taurine deficiency occurred in the low dietary sulfer-containing amino acids

9. Methionine→ cysteine→ cysteine sulphinic acid →hypotaurine →taurine

10. Structure of protein • Primary structure = linkage between α-carboxyl of one amino acid group of another (peptide linkage)

11. Secondary structure = polypeptide in the form of a α-helix by means of hydrogen bond CO—HN. α—helix or β—pleated sheet, supercoil

12. Tertiary structure : polypeptide into a globular form by means of: • hydrophobic • disulfide linkage (s-s) • salt bridge • hydrogen bonding a globular form

13. Quaternary structure alignment of several tertiary structure into one protein by means of hydrogen bonds, electrostatic, salt bonds Ex: hemoglobin consist of four single strand tertiary.

14. Gastrointestinal microflora synthesize protein from nonprotein N sources. • The length of the chain and the order of arrangement of amino acids within the chain are two of the main factors determining the characteristics of the protein.

15. Synthesis of protein from amino acids. The linkage between amino acids called peptide bond. Elongation of chain from tripeptide, polypeptide. • All naturally occuring amino acid are in the L-form. which is the biologically active form. (但合成大多為L與D form的混合物).

16. All proteins can be classified on the basis of their shape; their solubilities in water, salt, acids, bases and alcohol; and other special characteristics.

17. Egg albumin is the most perfect protein for meeting animal need because of its nearly ideal amino acid composition and its high digestibility. • Corn endosperm: Zein(玉米蛋白) is low in lysine and tryptophan. Opaque-2 corn is lower contain in zein, 此種玉米含較高量之lysine及tryptophan.

18. A sensitive measure of the nutritive value of protein is the balance among its essential balance, no two protin have an identical amino acid composition.

19. Lipoprotein • Represented by the menbrane proteins of animal cells. • myelin: in nervous system mucolipid erythrocyte membrane • The protein content of plasma lipoprotein ranges from 2% in chylomicron to about 50% in high density lipoprotein.

20. Glycoprotein • Chondroitin sulfate A. B. C. (protein complex of sulfated polysaccharides)出現在cartilage, tendon and skin. • Mucoprotein: complex of protein with: • amino sugar (glucosamine, galactosamine.) • hexose, manose, galactose. • pentose, fucose • sialic acid

21. Glycoprotein • serum cholinesterase • gonadotrophin(性腺素) • mucous secretion • ovalbumin (mucoprotein containing glucosamine, mannose). • ovomucoid (containing hexosamine, hexose; trypsin inhibitor in egg white) • aspartic acid (是主要與醣類結合之胺基酸)

22. Functions • Present as components of cell membrane, muscle, skin, hair, hooves, blood plasma protein, enzyme, hormones, immune antibody.

23. Tissue protein • Collagen: triple helix, 含proline, hydroxylproline • Elastin: resemble denatured collagen and consist of long, randomly ordered, ploy-peptide chain. minor component of musculature. • myofibrilar protein : the proteins of sacroplasm.(肌肉與稀鹽類均質後可萃取﹐含有20種酵素) • contractile protein : three protein- actin, tropomyosin B and myosin. 與muscle contraction有關.

24. Tissue protein • Keratins : proteins of hair, wool, feathers, hooves, horns, claws, beaks. • Blood proteins : albumin and a series of globulins, apoprotein • Enzymes : hydrolytic and degradative metabolic and synthetic reaction. • Hormones : insulin, growth hormone, gonadotrophic hormone, parathyroid hormone and calcitonin。

25. Metabolically active peptides and polypeptides • A large number of peptides and poly-peptide been identified in modulating growth and other metabolic activity. • such as • insulin-like growth factor (IGF-1,) • transforming growth factor beta (TGF-B) • fibroblast growth factor (FGF) • nerve growth factor (NGF)

26. Metabolism • two phases: catabolism (degradation) and anabolism (synthesis) • The conversion of dietary protein to tissue protein involves: • Intact dietary protein hydrolysis in GI tract (catabolism) • Amino acid in intestinal lumen absorption from GI tract • Amino acid in blood synthesis in tissues (anabolism) • Intact tissue proteins

27. Even protein hydrolyzed easily in the GI tract do not have a high nutritional value, if they have a deficiency or an unbalance of one or more amino acids. • Dietary protein not containing the proportion of essential amino acids to meet the animal needs cannot be used efficiently for tissue protein synthesis.

28. Digestion • Protein→→→ tripeptide, dipeptide, amino acid( lumen) → absorption → brush border enzyme (dipeptidase, tripeptidase) → dipeptidase, tripeptidase in enterocycte → amino acids Hydrolysis determine the degree of absorption of amino acid

29. (A) Digestible protein refer to that disappearing from the ingesta as it passes down the GI tract. • Nitrogen in feces include: • Unabsorbed dietary N . • Metabolic fecal N Metabolic fecal N : 1.Normal metabolism of tissue protein cells 2.sloughed residue of digestive enzyme. 3.other substrate secreted into the lumen.

30. (B) After absorption, amino acid are subject to further losses in utilization through metabolism in the liver and other tissues. losses N mainly as urinary urea N (mammal), or uric acid (bird).

31. (C) The degree of utilization of feed protein depend on • digestibility, absorbability • utilization of its component amino acids after absorption.

32. Absorption of amino acids 1. early postnatal life: • absorbed by pinocytosis. (如immune globulins and lactoferrin) 2. postnatal life: • absorbed by active transport ( two system ) • one for neutral amino acid. • one for basic amino acid. • 相關性質之amino acid由於競爭carrier, 吸收會受抑制。如leucine與 isoleucine methionine與lysine. 3. peptide are absorbed directly from the rumen and omasum

33. Fate of amino acids after absorption • tissue protein synthesis • synthesis enzyme, hormone and metabolites • deamination or transamination and use of the carbon skeleton for energy.

34. Amino acid in the GI have three source: • 1.Dietary ingestion • 2.recycle from other nitrogen substance( digestive enzyme, sloughed mucosa cell) • 3.synthesized by microorganism

35. A. Synthesis by microorganism • Bacteria, protozoans can synthesis all amino acids in presence of ammonia, S, carbon sources • Rumen, large intestine • In ruminant, synthesis amino acid from nonprotein nitrogen. B. Body tissue Tissue synthesis and degradation of amino acid in animal. Muscle, liver, brain, adipose tissue and others…..

36. Sites of amino acid degradation • Microbes, cell and tissue specific pathways degrade all amino acids, • Liver is the principle organ, and small intestinal cells to process of degradation. • Transamination, decarboxylation, hydroxylation . • Product of degradation: amionia, S, fatty acids (VFA). CO2

37. Nitrogen cycling in the intestine • Dietary nitrogen→intestine →blood • Endogenous N (urea) →intestinal lumen →microbial action →NH3 →used for incorporation into amino acids to produce microbial protein →digested by host

38. NO in animal nutrition and health • Nitric oxide is a mediator of immune function, a neurotransmitter, a signaling molecule, and endothelium-derived relaxing factor and other positive role in metabolism. • It is a cytotoxic free radical. • Is synthesized from arginine through action of the enzyme nitric oxide synthase (NOS). • Many nutrient, including protein and amino acid may modulate NO production by NOS.

39. Ruminant nitrogen metabolism • RUP: rumen undegraded protein

42. Synthesis of protein DNA (chromosomal component of cell) │ carry the genetic information ↓ transcript into a strand of messenger RNA ↓ tranlation of mRNA into protein

43. Whole body protein turnover • Is a dynamic process involving continuous and simultaneous protein synthesis and protein degradation. • Each organ or tissue has its own rate of protein turnover. • The rate of body muscle growth is affected by the rate of protein synthesis relative to degradation.

44. Deamination and Transamination • Deamination :removal of the amino group from carbon of amino acid and entrance of the amino group into the urea. • Transamination: transfer an amino group from one amino acid to the carbon of a keto acid.

45. Urea cycle • The urea or ornithine cycle is a key metabolic phenomenon in protein metabolism. • Uric acid is end product of purine metabolism in human and other primate, in other mammals the principal end product is the oxidation product of uric acid, allantoin.

49. Protein and amino acid requirement and deficiency • Nonruminant (pig, chichken, human) require essential amino acid. • Nonruminant herbivores, and adult ruminant depend on nonprotein N and synthesize protein or amino acid. • Adult ruminant (cattle, sheep) can depend entirely on nonprotein N in the diet by virtue of their rumen microbes.

50. Because most energy sources are low in protein and protein supplement are expensive, so inadequate protein is the most common. • protein is diverted to energy only when it is provide in excess of the metabolic requirement or calorie intake is insufficient.