Peptides (1. LF UK, NT)

Structure

condensation (amino acids -› peptides)

File:Formation of cyclic dipeptide.jpg

binding of some amino acids in an unusual way (Glu distal group COOH = γ-peptide bond)
bound D-amino acids
unusual amino acids bound
- ß-alanine (3-aminopropionic) File:Beta-alanine.jpg, α-aminobutyric (2-aminobutyric) File:Alpha-aminobutyric.jpg, γ-aminobutyric (4-aminobutyric) File:Gamma-aminobutyric.jpg, taurine File:Taurine.jpg, 2-aminoacrylic (dehydroalanine ) File:2-aminoacrylic.jpg, (E)-2-aminocroton (dehydrobutyrin) File:Dehydrobutyrin.jpg, pyroglutam File:Pyroglutam.jpg

Classification[edit | edit source]

Number of bound monomers (amino acids)

oligopeptides (2–10 amino acids)
polypeptides (formerly macropeptides, 11–100 amino acids)

String type

linear
cyclical

type of bonds

homodet (peptide bonds only)
heterodet (peptide and other bonds)
- disulfide -S-S-, ester (depsipeptides) -CO-O-R

Bound folders

homeomeric containing only amino acids
heteromeric (peptoids) containing also other compounds
- nucleopeptides – phosphopeptides
- lipopeptides – chromopeptides
- glycopeptides – metallopeptides

Occurrence[edit | edit source]

products of metabolism, natural peptides
products of proteolysis, enzymatic or non-enzymatic hydrolysis
synthetic peptides, substitute sweeteners

Properties[edit | edit source]

biological activity
sensory properties
products of metabolism of lactic acid bacteria = bacteriocins
nisin (Streptococcus cremoris, syn. Lactococcus lactis ssp. Lactis)
preservative, stabilization of fermented products

Significant Peptides[edit | edit source]

Glutathione[edit | edit source]

(G-SH or G-S-S-G) γ-L-glutamyl-L-cysteinylglycine (γ-amide bond) File:Glutathione.jpg

Occurrence

microorganisms, plants, animals
- wheat flour (10-15 mg/kg)
- meat (300-1500 mg/kg)

Function

detoxification of toxic forms of oxygenu
transport (transfer) of amino acids into cells
metabolic processes (leukotriene biosynthesis)
stabilization of the oxidation state of SH-proteins (substrate of peroxidase, glutathione reductase)
technology

Chorleywood method of white bread production, ascorbic acid

H₂A + ½ O₂ → A + H₂O (ascorbase)
A + 2 G-SH → H₂A + G-S-S-G (glutathione dehydrogenase)
G-S-S-G – without affecting the rheological properties of the dough
G-SH – negative effect (gluten protein depolymerization)
P-S-S-P + G-SH → P-S-S-G + P-SH

β-alanylhistidine dipeptides[edit | edit source]

carnosine File:Karnosine.jpg, anserin File:Anserin.jpg, balenin File:Balenin.jpg

Occurrence

in meat

Function

participation in contraction of skeletal muscle
buffering capacity of the muscle
organoleptic properties

Products of proteolysis

spontaneous proteolysis (autolysis)
- desired maturation of meat (consistency, aroma), production of yeast autolysates (additives)
- undesirable
intentional proteolysis
- cheese production (desired consistency, aroma)
- production of malt (stabilization of beer foam)
- production of protein hydrolysates
  - Enzymatic:
    - soy sauce
    - hydrolysates of waste proteins (blood, whey, caseins)
  - sour: soup spices and other preparations

Bitter peptides of enzyme hydrolysates and foods[edit | edit source]

hydrophobic amino acids: Val, Leu, Ile, Phe, Tyr, Trp (M < 6000 Da)

Synthetic Peptides[edit | edit source]

substitute sweetener Aspartame (Asp-Phe) File:Aspartame.jpg

Links[edit | edit source]

Source[edit | edit source]

{{#switch: web

|book =

  Incomplete publication citation. Also available from <https://el.lf1.cuni.cz/p51525121/>.

|collection =

  Incomplete citation of contribution in proceedings. . Also available from <https://el.lf1.cuni.cz/p51525121/>. {{
  #if:  |978-80-7262-438-6} }
  |article = 
  Incomplete article citation.  . 2. AMINO ACIDS, PEPTIDES, PROTEINS. also available from <https://el.lf1.cuni.cz/p51525121/>.

|web =

  Incomplete site citation. . 2. AMINO ACIDS, PEPTIDES, PROTEINS [online]. [cit. 2012-03-10]. <https://el.lf1.cuni.cz/p51525121/>.

|cd =

  Incomplete carrier citation. . 2. AMINO ACIDS, PEPTIDES, PROTEINS [CD/DVD]. [cit. 2012-03-10].

|db =

  Incomplete database citation. 2. AMINO ACIDS, PEPTIDES, PROTEINS [database]. [cit. 2012-03-10]. <https://el.lf1.cuni.cz/p51525121/>.

|corporate_literature =

  Incomplete citation of company literature. . Also available from <https://el.lf1.cuni.cz/p51525121/>. legislative_document = 
  Incomplete citation of legislative document.  Also available from URL <https://el.lf1.cuni.cz/p51525121/>.

References[edit | edit source]