Basic Amino Acids
Basic amino acids are a group of amino acids that have a positively charged side chain at physiological pH. This charge is due to the presence of an amino group in their side chains. Examples of basic amino acids include lysine, arginine, and histidine. These amino acids play important roles in protein structure and function, as well as in various biochemical processes within the body.
7 Key excerpts on "Basic Amino Acids"
eBook - ePubBiochemistry
An Organic Chemistry Approach
- Michael B. Smith(Author)
- 2020(Publication Date)
- CRC Press(Publisher)
...11 Amino Acids There is an important class of difunctional molecule that is critical to an understanding of biological processes. Amino acids comprise the backbone of peptides, and thereby of enzymes. This chapter will discuss the structure, nomenclature, and characteristics of amino acids. 11.1 Characteristics of Amino Acids An amino acid, as the name implies, has one amine unit (–NR 2) and one carboxylic acid unit (a carboxyl group, COOH). The nomenclature for a generic amino acid is dominated by the carboxyl, so the parent name is “acid” and the NR 2 unit is treated as a substituent. When an amine unit is a substituent the name “amino” is used, so these compounds are amino carboxylic acids, or just amino acids. Amino acids are easily named using IUPAC nomenclature and the carboxylic acid is the parent for each new compound. Two examples are 2-aminopropanoic acid (known as alanine) and 5-amino-3,5-dimethylheptanoic acid. There are a variety of structural variations for amino acids. If the amine unit is attached to C2, the α-carbon of the carboxylic acid chain, the compound is an α-amino acid. If the amine group is on C3, the β-carbon it is a β-amino acid. Similarly, there are γ-amino acids, δ-amino acids, and so on. Due to their biological importance, α-amino acids will be discussed most of the time. The common names of α-amino acids are presented in Table 11.1 in Section 11.2. To distinguish α-amino acids from other amino acids, the term non-α-amino acids is used. 5-Amino-3,5-dimethylheptanoic acid is a non-α-amino acid, for example. Table 11.1 Structures, Names, Three-Letter Code and One-Letter Code of the 20 Essential Amino Acids, Based on the Structure in Figure 11.5 R Name Three-Letter Code One-Letter...
eBook - ePub- S. P. Bhutani(Author)
- 2019(Publication Date)
- CRC Press(Publisher)
...That means they have the same relative configuration as L -glyceraldehyde. As the two functional groups present in amino acids are acidic and basic, all amino acids are amphoteric and actually exist as zwitterions. Thus, the simplest amino acid glycine exists in the form shown below rather than aminoacetic acid. H 2 N—CH 2 — COOH ⇄ H 3 N + — CH 2 — CO O ¯ Aminoacetic acid Zwitterion 2.3 CLASSIFICATION OF AMINO ACIDS The 22 α-amino acids that are obtained from proteins can be classified into four different groups on the basis of the structures of their side chains: 1. Neutral Amino Acids 2. Acidic Amino Acids 3. Neutral Amino Acids with Polar Side Chains 4. Basic Amino Acids These are listed with their symbols, abbreviations and structures in Table 2.1. Only 20 of the 22 amino acids listed in Table 2.1 are actually used by cells when they synthesise proteins. Hydroxyproline is synthesised from proline and cystine is synthesised from cysteine. Asparagine and glutamine are derived from aspartic acid and glutamic acid. TABLE 2.1 Amino Acids Commonly Found in Proteins 2.4 THE ESSENTIAL AMINO ACIDS Amino acids are synthesised by all living organisms, animals and plants for their protein requirements. The biosynthesis of proteins requires the presence of all the constitutent amino acids. If one of the 20 amino acids is missing or in short supply, protein biosynthesis is inhibited. Some organisms, such as E.Coli can synthesise all the amino acids that they need. However, the human body is unable to synthesise some of these amino acids required for making proteins. These are called essential amino acids. For adult humans there are ten amino acids, which have been designated with the superscript e in Table 2.1. They must be included in our diet. We eat proteins, break them down in our body to their constituent amino acids and then use some of these amino acids to build up other proteins which we require to maintain good health...
eBook - ePubBiochemistry Explained
A Practical Guide to Learning Biochemistry
- Thomas Millar(Author)
- 2018(Publication Date)
- CRC Press(Publisher)
...4 Amino Acids and their Functions In this chapter you will learn: the functional groups: an amine and carboxyl groups to understand the general structure of amino acid the structures, names and single letter symbols for the 20 amino acids found in proteins how 2 cysteines may be oxidised to form the bridging amino acid cystine how the carbons of amino acids are named or numbered the terms ampholyte and zwitterion and how these relate to amino acids the structure of an amide bond and the special case a peptide bond special functions of amino acids (e.g. neurotransmitters) and structural relationships between amino acids how ketones are formed from amino acids by removing ammonia from the αC the synthesis of the bioactive amines dopamine, noradrenaline, adrenaline and serotonin. to understand the basis for Parkinson’s disease and phenylketonuria that tyrosine, serine and threonine are phosphorylation sites in proteins the importance of decarboxylation in the formation of some active amines such as histamine how sugars may attach to the amino acids serine, threonine and asparagine Basic structure and nomencalture of amino acids The name amino acid suggests that these structures have an amine and an acid group. Indeed this is true; amino acids have an amino group and a carboxylic acid. The structure of a typical L-amino acid is illustrated below. This type of amino acid is the basis of proteins. Q&A 1 : Draw the chemical structures of a carboxylic acid, and an amine group. There is a central carbon that has bonds to an amine group, a carboxylic acid, an hydrogen and a variable R group. Since this central carbon has 4 different groups attached to it, it is a chiral carbon and hence there are 2 possible isomers, L and D. Nearly all amino acids in biochemistry are of the L-form (L for life). Note that this is the opposite of sugars, which nearly always occur as the D isomer. You need to learn their structure in this orientation...
eBook - ePub- Raymond S. Ochs(Author)
- 2021(Publication Date)
- CRC Press(Publisher)
...5 Amino Acids and Proteins The word protein is of Greek origin, meaning “first place” or primary. Berzelius originated this term in 1838 to identify a substance found in plant fibers essential for animal nutrition. This identification was well before the molecular nature of proteins was discovered. Proteins are the most diverse of biomolecules. They include structural proteins (such as the plant fibers), binding proteins (such as hemoglobin), and enzymes (such as sucrase). In this chapter, we examine protein structure and some elements of their binding behavior. In the next, we examine their function as enzymes. The proteins also play a central role in all subsequent chapters of the book, commensurate with their paramount importance in biochemistry. 5.1 Common Structure of the Amino Acids All amino acids contain an amine group (most commonly a primary amine) and a carboxyl group (the acid portion) attached to the same carbon. The latter is called the α-carbon, from an organic chemistry nomenclature system that assigns Greek letters to carbons adjacent to carboxyl groups: α, β, etc (Figure 5.1). Note that this is a distinctive use of the Greek lettering system from the carbohydrates. Also bound to the α-carbon is a hydrogen atom (the α-hydrogen) and a variable group designated as R (Figure 5.2). Twenty different R groups make up the common amino acids, meaning those incorporated into proteins. Except for glycine (for which R is a hydrogen atom), the α-carbon is chiral and designated as l or d by comparison to the reference molecule glyceraldehyde, illustrated in Figure 5.3 for the case of alanine (in which R is –CH 3). The carboxyl group of alanine is most similar to the carbonyl group of glyceraldehyde. The amine group of alanine is most similar to the OH group of glyceraldehyde. In nature, virtually all amino acids are present in the l form. FIGURE 5.1 Organic carboxyl bearing chain numbering...
eBook - ePub- Raja Sivamani, Jared R. Jagdeo, Peter Elsner, Howard I. Maibach, Raja Sivamani, Jared R. Jagdeo, Peter Elsner, Howard I. Maibach(Authors)
- 2015(Publication Date)
- CRC Press(Publisher)
...Chapter 15 Amino Acids and Derivatives Kazutami Sakamoto Introduction Amino acids are molecules with both an amino group and carboxylic group. There are 20 kinds of naturally occurring amino acids with optical active structures at α-position (L-amino acids) except glycine. Greenstein and Winitz said: “Few products of natural origin are versatile in their behavior and properties as are the amino acids, and few have such a variety of biological duties to perform” in their preface of Chemistry of the Amino Acid in 1961. 1 Subsequently significant progress has been made on the knowledge of amino acids, and technical achievements to utilize such progress are remarkable, including cosmetic and cosmeceutical applications. This is due to the market growth and cost reduction of certain amino acids for many industrial applications. For example, in food applications there is huge and still growing consumption generated for glutamic acid (Glu) and glycine (Gly) as food additives and aspartic acid (Asp) and phenylalanine (Phe) as raw materials for the artificial sweetener “aspartame.” Consumption of lysine (Lys), methionine (Met), and threonine (Thr) is expanding in the animal food additives market. Cysteine (CysH) and proline (Pro) are major amino acids utilized in the flavor industry to manufacture natural flavors by Maillard reaction with sugars. Health food and pharmaceutical intermediates are other rapidly growing markets for many amino acids...
eBook - ePubEat Your Vitamins
Your Guide to Using Natural Foods to Get the Vitamins, Minerals, and Nutrients Your Body Needs
- Mascha Davis(Author)
- 2020(Publication Date)
- Adams Media(Publisher)
...Amino Acids, Essential (Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, and Valine) Amino acids (AA) are the building blocks of protein. Protein is one of the three essential macronutrients, along with carbohydrates and fat, that you need to consume daily. Your body can make some amino acids but others you have to get from the foods you eat. Out of twenty total amino acids in your body, there are nine that are essential. They are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. Three of these essential AAs are called branched-chain amino acids (BCAAs) and are covered in the previous section, “Amino Acids, Branched Chain.” Description Amino acids are classified by whether or not they can be made by the body. Out of the twenty AAs that you use to make proteins, you need to get nine from the foods you eat; these are classified as “essential.” Of the remaining eleven, five are considered “nonessential,” meaning you can create them without having to eat them, and six are considered “conditionally essential,” because you can only make them if you consume enough protein and other nutrients. In times of increased need, such as during severe illness, injury, or other stress to the body, you may need to consume these conditionally essential AAs like you would essential AAs. In a nutshell: The nine essential amino acids are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. The six conditionally essential amino acids are arginine (this AA is actually essential for children), cysteine, glutamine, glycine, proline, and tyrosine. The five nonessential amino acids are alanine, asparagine, aspartic acid, glutamic acid, and serine. Role in the Body Muscle creation and maintenance: Amino acids are the building blocks of proteins, which make up your muscles and tissues...
eBook - ePub- Guoyao Wu(Author)
- 2017(Publication Date)
- CRC Press(Publisher)
...4 Chemistry of Protein and Amino Acids The word “protein” originated from the Greek word “proteios,” meaning prime or primary (Meister 1965). A protein is a large polymer of amino acids (AAs) linked via the peptide bond (–CO–NH–). Different proteins have different chemical properties (e.g., AA sequences, molecular weights, ionic charges, three-dimensional (3D) structures, hydrophobicity, and function). The general structure of an AA is shown in Figure 4.1. There may be one or more polypeptide chains in a protein, which contains its constituents (nitrogen, carbon, oxygen, hydrogen, and sulfur atoms). A protein may be covalently bonded to other atoms and molecules (e.g., phosphates) and non-covalently attached with minerals (e.g., calcium, iron, copper, zinc, magnesium, and manganese), certain vitamins (e.g., vitamin B 6, vitamin B 12, and lipid-soluble vitamins), and/or lipids. Protein is the major nitrogenous macronutrient in foods and the fundamental component of animal tissues (Wu 2016). It has structural, signaling, and physiological functions in animals (Table 4.1). Figure 4.1 Fisher projections for configurations of AAs relative to l - and d -glyceraldehydes. The general structure of an AA in the non-ionized form is shown...
