Legumin is family of globular

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...

s obtained from

beans A bean is the seed of several plants in the family Fabaceae, which are used as vegetables for human or animal food. They can be cooked in many different ways, including boiling, frying, and baking, and are used in many traditional dishes th ...

peas The pea is most commonly the small spherical seed or the seed-pod of the flowering plant species ''Pisum sativum''. Each pod contains several peas, which can be green or yellow. Botanically, pea pods are fruit, since they contain seeds and d ...

lentils The lentil (''Lens culinaris'' or ''Lens esculenta'') is an edible legume. It is an annual plant known for its lens-shaped seeds. It is about tall, and the seeds grow in pods, usually with two seeds in each. As a food crop, the largest produ ...

vetches ''Vicia'' is a genus of over 240 species of flowering plants that are part of the legume family ( Fabaceae), and which are commonly known as vetches. Member species are native to Europe, North America, South America, Asia and Africa. Some othe ...

hemp Hemp, or industrial hemp, is a botanical class of ''Cannabis sativa'' cultivars grown specifically for industrial or medicinal use. It can be used to make a wide range of products. Along with bamboo, hemp is among the fastest growing plants o ...

(specifically

edestin Edestin, (also known as Edistin) is a highly-digestible, hexameric legumin protein with six subunits, and a seed storage protein, with a molecular weight of 310 kDa. This protein is primarily found in hemp seeds. Edestin is a globular protein (bio ...

) and other leguminous seeds. Edestin is a biologically active legumin protein that is digestible for human bodies. Garden peas are a common nutritional source for humans that contains legumin. Legumin is similar to the

casein Casein ( , from Latin ''caseus'' "cheese") is a family of related phosphoproteins (CSN1S1, αS1, aS2, CSN2, β, K-casein, κ) that are commonly found in mammalian milk, comprising about 80% of the proteins in cow's milk and between 20% and 60% of ...

of mammalian milk and was called "vegetable casein" since it was considered analogous to the mammalian protein. The primary function of the legumin protein in seeds is storage. Legumin proteins are one of the main storage proteins of

angiosperms Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants th ...

and

gymnosperm The gymnosperms ( lit. revealed seeds) are a group of seed-producing plants that includes conifers, cycads, ''Ginkgo'', and gnetophytes, forming the clade Gymnospermae. The term ''gymnosperm'' comes from the composite word in el, γυμνό� ...

s. Legumin is an insoluble hexameric

conjugated protein A conjugated protein is a protein that functions in interaction with other (non-polypeptide) chemical groups attached by covalent bonding or weak interactions. Many proteins contain only amino acids and no other chemical groups, and they are ca ...

with a high concentration of carbon and oxygen.

Properties

Structure

Legumin is a conjugated protein with six subunits. The individual subunits have a hydrophilic α chain that is initially linked to the smaller hydrophobic β chain with a peptide bond. Both the α and β chains are encoded by the same gene. Each of the six subunits has a mass of ~50-60 kDa. During

translation Translation is the communication of the Meaning (linguistic), meaning of a #Source and target languages, source-language text by means of an Dynamic and formal equivalence, equivalent #Source and target languages, target-language text. The ...

of the α and β chains, the polypeptide is inserted into the

endoplasmic reticulum The endoplasmic reticulum (ER) is, in essence, the transportation system of the eukaryotic cell, and has many other important functions such as protein folding. It is a type of organelle made up of two subunits – rough endoplasmic reticulum ( ...

(ER) where the

signal peptide A signal peptide (sometimes referred to as signal sequence, targeting signal, localization signal, localization sequence, transit peptide, leader sequence or leader peptide) is a short peptide (usually 16-30 amino acids long) present at the N-ter ...

that initiated the cell to translocate the chains is cleaved. A disulfide bridge is formed between the α and β chains to form prolegumin, a

protein precursor A protein precursor, also called a pro-protein or pro-peptide, is an inactive protein (or peptide) that can be turned into an active form by post-translational modification, such as breaking off a piece of the molecule or adding on another molecule ...

. Three of these subunits come together to form a trimer in the ER. The trimer of prolegumins can be transported to the vacuole for further

post-translational modification Post-translational modification (PTM) is the covalent and generally enzymatic modification of proteins following protein biosynthesis. This process occurs in the endoplasmic reticulum and the golgi apparatus. Proteins are synthesized by ribosome ...

. In the vacuole, the peptide bond formed between the α and β chains is cleaved now that the disulfide bridge holds the two chains together. The cleavage of the α and β chains within the trimers signals protein maturation where two trimers to come together and form the final hexameric legumin protein.

Composition

Although legumin is similar to casein of mammalian milk but it contains less carbon and more nitrogen than true casein.

Karl Heinrich Ritthausen Karl Heinrich Ritthausen (13 January 1826 – 16 October 1912) was a German biochemist who identified two amino acids and made other contributions to the science of plant proteins. Education Ritthausen was born in Armenruh, near Goldburg, Sil ...

found legumin from peas, vetches, lentils, and field beans to contain the elements in the following proportions: carbon, 51.48%; hydrogen, 7.02%; nitrogen, 16.77%; and oxygen, 24.32%. When treated with

sulfuric acid Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid ( Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen and hydrogen, with the molecular formu ...

, legumin breaks down to

leucine Leucine (symbol Leu or L) is an essential amino acid that is used in the biosynthesis of proteins. Leucine is an α-amino acid, meaning it contains an α-amino group (which is in the protonated −NH3+ form under biological conditions), an α- ca ...

tyrosine -Tyrosine or tyrosine (symbol Tyr or Y) or 4-hydroxyphenylalanine is one of the 20 standard amino acids that are used by cells to synthesize proteins. It is a non-essential amino acid with a polar side group. The word "tyrosine" is from the Gr ...

, and glutamic and

aspartic acid Aspartic acid (symbol Asp or D; the ionic form is known as aspartate), is an α-amino acid that is used in the biosynthesis of proteins. Like all other amino acids, it contains an amino group and a carboxylic acid. Its α-amino group is in the pro ...

s. Legumin proteins are relevant because their composition as a storage protein means they are a highly biologically active source of protein. Legumes like beans, lupins, and peas have great nutritional value for humans. They provide an inexpensive but effective low fat protein source. Although peas are commonly consumed as a source leguminous protein, lupins and soybeans provide a much higher protein content. Legumes are also a rich source of essential amino acids.

Solubility

Legumin proteins are insoluble in water because of their hydrophobic units. Legumins are soluble in very weak

acid In computer science, ACID ( atomicity, consistency, isolation, durability) is a set of properties of database transactions intended to guarantee data validity despite errors, power failures, and other mishaps. In the context of databases, a sequ ...

s and

alkalies In chemistry, an alkali (; from ar, القلوي, al-qaly, lit=ashes of the saltwort) is a basic, ionic salt of an alkali metal or an alkaline earth metal. An alkali can also be defined as a base that dissolves in water. A solution of a ...

. This protein it is not

coagulate Coagulation, also known as clotting, is the process by which blood changes from a liquid to a gel, forming a blood clot. It potentially results in hemostasis, the cessation of blood loss from a damaged vessel, followed by repair. The mechanism o ...

d by heat. Due to their important storage function legumin proteins and another important storage protein vicilin have been found be to the most abundant water and alkali soluble proteins within cottonseed.

References

{{reflist Seed storage proteins

Properties

Structure

Composition

Solubility

See also

Similar and Related Proteins

References