Lesson 2.4. Protein Classification

Albumins

Based on the composition / hydrolysate: Simple Proteins

• soluble in water and is coagulated by heat

ovalbumin

Examples of albumins found in egg whites

lactalbumin

Examples of albumins found in milk

myogen

Examples of albumins found in muscle

serum albumin

Examples of albumins found in blood

legumelin

Examples of albumins found in peas

Globulins

Based on the composition / hydrolysate: Simple Proteins

• It is insoluble in water but soluble in dilute salt solutions and is coagulated by heat

ovoglobulin

example of globulins found in egg white

lactoglobulin

example of globulins found in milk

serum globulin

example of globulins found in blood

legumin

example of globulins found in peas

arachin

example of globulins found in peanuts

phaseolin

example of globulins found in beans

amadin

example of globulins found in almonds

Glutelins

Based on the composition / hydrolysate: Simple Proteins

• only from plants

• It is insoluble in water and neutral salt solutions but soluble in dilute acids/ bases. It is coagulated by heat.

glutenin

example of glutelins found in wheat

oryzenin

example of glutelins found in rice

Prolamines

Based on the composition / hydrolysate: Simple Proteins

• found mostly in plants

• It is insoluble in water and absolute alcohol but soluble in 70-80% alcohol

zein

example of prolamines found in corn

gliadin

example of prolamines found in wheat

Albuminoids / Schleroproteins

Based on the composition / hydrolysate: Simple Proteins

• only from animals

• It the least of all proteins; insoluble in all the solvents mentioned previously

keratin

example of Albuminoids / Schleroproteins found in hair, hooves, nails/claws, horns, and feathers)

collagen

example of Albuminoids / Schleroproteins found in bones and skin

elastin

example of Albuminoids / Schleroproteins found in tendons

fibroin

example of Albuminoids / Schleroproteins found in silkworms

Histones

Based on the composition / hydrolysate: Simple Proteins

• It is insoluble in dilute NH4OH but soluble in water and dilute acids. It is not coagulated by heat

globin

example of Histones found in hemoglobin

thymus histone

example of Histones found in thymus gland

gadus

example of Histones found in codfish

scombrone

example of Histones found in mackerel

Protamines

Based on the composition / hydrolysate: Simple Proteins

• It is the simplest in structure. It is soluble in water, dilute acids, and NH4OH. It is not coagulate by heat.

salmine

example of Protamines found in salmon

sturine

example of Protamines found in fish sperm

scombrine

example of Protamines found in mackerel

cyprinine

example of Protamines found in carp

chyprine

example of Protamines found in herring

Nucleoproteins

Based on the composition / hydrolysate: Conjugated Proteins

• It is found in the nuclei of living cells linked with nucleic acids.

nucleoprotamine

ex of Nucleoproteins (nucleic acid + protamine)

nucleohistone

ex of Nucleoproteins (nucleic acid + histone)

Glycoproteins

Based on the composition / hydrolysate: Conjugated Proteins

• It is linked with carbohydrates

mucin

ex of glycoproteins found in saliva

mucoids

ex of glycoproteins found in tendons, cartilage

ovomucoid

ex of glycoproteins found in egg white

serum mucoid

ex of glycoproteins found in blood

urine mucoid

ex of glycoproteins found in urine

Phosphoproteins

Based on the composition / hydrolysate: Conjugated Proteins

• It is linked with phosphoric acid.

casein

ex of phosphoproteins found in milk

vitelline

ex of phosphoproteins found in egg yolk

Chromoproteins

Based on the composition / hydrolysate: Conjugated Proteins

• It is linked color-producing group

hemoglobin

ex of chromoproteins found in blood

melanin

ex of chromoproteins found in hair, feathers

flavoproteins

ex of chromoproteins found in rhodopsin

cytochrome

ex of chromoproteins

Lipoproteins

Based on the composition / hydrolysate: Conjugated Proteins

• It is linked with fatty acid group

hemoglobin

ex of Lipoproteins found in blood

protein in egg yolk, milk, cell nuclei/membrane

ex of Lipoproteins

Metalloproteins

Based on the composition / hydrolysate: Conjugated Proteins

• It is linked with metals (heavy metals)

Mg, Co, Zn, Mn, Cu

ex of Metalloproteins

Primary derived proteins

those which the size of the protein is not materially altered from the action of heat, acids/bases, or enzymes

Proteans

Based on the composition / hydrolysate: Primary Derived Proteins

• It is insoluble in water. These are the first products formed from the action of acids, enzymes, or water on proteins.

Metaproteins

Based on the composition / hydrolysate: Primary Derived Proteins

• It is insoluble in water but soluble in dilute acids/bases. They are produced from further action of acids/bases on proteins.

Coagulated proteins

Based on the composition / hydrolysate: Primary Derived Proteins

• These are insoluble protein products produced by the action of heat or alcohol on proteins.

Secondary derived proteins

those in which definite hydrolysis have taken place producing products smaller than the original protein

Proteoses

Based on the composition / hydrolysate: Secondary Derived Proteins

• It soluble in water, coagulated with heat, and precipitated by saturating solution with NH4SO4.

Peptones

Based on the composition / hydrolysate: Secondary Derived Proteins

• Exactly similar to proteoses in terms of properties except that they are not precipitated by NH4SO4.

Peptides

Based on the composition / hydrolysate: Secondary Derived Proteins

• Simplest of all derived proteins. It can be di/tri/tetra- depending on the number of AA residue in the molecule.

Fibrous

Based on the structure

• It is insoluble in water. Polypeptides arrange tightly in parallel fibers or sheets making up the structural framework of the body.

collagen

ex of fibrous proteins that is insoluble but may be boiled to form gelatin; it is the most abundant in humans

elastin

ex of fibrous proteins that is insoluble similar to collagen but it is not converted to gelatin. It is found in arteries, tendons, ligaments, and skin.

keratin

ex of fibrous proteins that is insoluble and indigestible fibrous protein found in hair, nails, claws, and feathers

Globular

Based on the structure

• These are polypeptides arranged in compact, spherical forms.

antibodies, hormones

ex of globular proteins

Mixed

Based on the structure

• It behaves like fibrous in terms of physical structure and strength but globular in terms of solubility

myosin, fibrinogen

ex of mixed proteins

Collagen

Based on the biological roles: Structural Protein

• Fibrous protein found in tendons/cartilages with high tensile strength

Elastin

Based on the biological roles: Structural Protein

• Structural protein capable of stretching in two dimensions commonly found in ligaments

Keratin

Based on the biological roles: Structural Protein

• Large, tough, and insoluble proteins found in hair, nails, fingernails, and feathers

Fiborin

Based on the biological roles: Structural Protein

• It is commonly found in silkworms and spider webs

Resilin

Based on the biological roles: Structural Protein

• It has perfect elastic property and are found in wing hinges of some insects

Glycoprotein

Based on the biological roles: Structural Protein

• Structural proteins acting as cell membranes and cell coats

Mucoprotein

Based on the biological roles: Structural Protein

• It is found in mucous membrane and synovial fluids

Schlerotin

Based on the biological roles: Structural Protein

• It is commonly found in the exoskeleton of insects

Alcohol dehydrogenase

Based on the biological roles: Catalytic Protein / Enzymes

• It facilitates alcohol fermentation in the body

Arginase

Based on the biological roles: Catalytic Protein / Enzymes

• It hydrolyzes arginine

Ribonuclease

Based on the biological roles: Catalytic Protein / Enzymes

• It hydrolyzes RNA

Urease

Based on the biological roles: Catalytic Protein / Enzymes

• It hydrolyzes urea forming CO2 + H2O.

Cytochrome C

Based on the biological roles: Catalytic Protein / Enzymes

• It facilitates the transport of electrons

Chymotrypsin

Based on the biological roles: Catalytic Protein / Enzymes

• It cleaves a polypeptide from the C-terminal of Arg and Lys

Trypsin

Based on the biological roles: Catalytic Protein / Enzymes

• It cleaves a polypeptide from the N-terminal of Arg and Lys

Rennin

Based on the biological roles: Catalytic Protein / Enzymes

• It is a digestive enzyme that acts on casein

Aminopolypeptidas

Based on the biological roles: Catalytic Protein / Enzymes

• It sequentially cleaves a polypeptide chain from the N-terminal

Ovalbumin

Based on the biological roles: Nutrient / Storage Protein

• It is the major protein in egg white

Casein

Based on the biological roles: Nutrient / Storage Protein

• It is the major protein in milk

Ferritin

Based on the biological roles: Nutrient / Storage Protein

• It stores iron in the spleen

Gliadin

Based on the biological roles: Nutrient / Storage Protein

• It is the seed storage in wheat

Zein

Based on the biological roles: Nutrient / Storage Protein

• It is the seed storage in corn

Thymus histone

Based on the biological roles: Nutrient / Storage Protein

• These are histones stores in the thymus gland

Hemoglobin

Based on the biological roles: Transport Protein

• It carries O2 from lungs to the different body organs

B1-lipoproteins

Based on the biological roles: Transport Protein

• It carries lipids from the liver to the other organs

Hemocyanin

Based on the biological roles: Transport Protein

• It transports O2 in the blood from some invertebrates