Amino Group
An amino group is a functional group in organic chemistry consisting of a nitrogen atom bonded to hydrogen atoms. It is commonly found in amino acids, the building blocks of proteins, and is responsible for the basic properties of these compounds. Amino groups can participate in various chemical reactions, making them important in the synthesis of many organic compounds.
8 Key excerpts on "Amino Group"
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 - 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- 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...
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- Lars Backman(Author)
- 2019(Publication Date)
- De Gruyter(Publisher)
...The three nitrogen atoms in the guanidinium group can all participate in ion–ion interactions as the charge is delocalized over the whole group. The guanidinium group also has several possibilities to act as acceptor and donor in hydrogen bond formation. The side chain Amino Group (ε-Amino Group) in lysine is rather reactive; it can form a Schiff base with aldehydes and it can be oxidized as well as hydroxylated. Table 3.1: Properties of α-amino acids. Free amino acid Protein Residue mass a p K a –COOH b p K a –NH2 b p K a side chain b p K a side. chain c Nonpolar Glycine 57.05 2.34 9.60 Alanine 71.08 2.34 9.69 Valine 99.13 2.32 9.62 Leucine 113.16 2.36 9.60 Isoleucine 113.16 2.36 9.60 Methionine 131.20 2.28 9.21 Proline 97.12 1.99 10.60 Polar-uncharged Serine 87.08 2.21 9.15 Threonine 101.11 2.09 9.10 Asparagine 114.11 2.02 8.80 Glutamine 128.13 2.17 9.13 Cysteine 103.15 1.96 10.28 8.18 6.8 ± −2.7 Polar-charged Aspartate 115.09 1.88 9.60 3.65 3.5 ± 1.2 Glutamate 129.12 2.19 9.67 4.25 4.2 ±. 0.9 Lysine 128.18 2.18 8.95 10.53 10.5 ± 1.1 Arginine 156.19 2.17 9.04 12.48 Histidine 137.14 1.82 9.17 6.00 6.6 ± 1.0 Aromatic Tryptophan 186.22 2.83 9.39 Tyrosine 163.18 2.20 9.11 10.07 10.5 ± 1.2 Phenylalanine 147.18 1.83 9.13 a The residue mass is the mass of the amino acid with an uncharged side chain in a protein. The molecular mass of an amino acid is obtained by adding 18 (the mass of water) to the residue mass. b p K a values of free amino acids are from CRC Handbook of Chemistry and Physics, 73rd edition. c p K a values of some side chains when present in proteins are from G.R Grimsley, J.M. Scholtz and N. Pace (2009) A summary of the measured p K a values of the ionizable groups in folded proteins, Prot Sci 18:247–251. Histidine is the only amino acid with a p K a close to neutral pH; the p K a of histidine is 6.0. Therefore, even relatively small changes in pH will change the average charge (Figure 3.9)...
eBook - ePub- S. P. Bhutani(Author)
- 2019(Publication Date)
- CRC Press(Publisher)
...The lone pair of electrons in the Amino Group is withdrawn by the acyl group attached to the nitrogen atom. The benzoyl derivatives are especially useful for characterisation. Condensation of amino acids with phthalic anhydride gives phthaloyl derivatives, which are of value in peptide synthesis. Sulphonamides result from the reaction with sulphonyl chloride. For example, iii. Nitrous Acid Reaction Nitrous acid reacts with amino acids to liberate one mole of nitrogen gas per mole of amino acid and gives the corresponding hydroxy acids. The reaction takes place with α–amino acids at room temperature in less than ten minutes and is of great utility for identification and assay of the purity of amino acids. The α-Amino Groups of lysine and arginine react in thirty minutes. The method and apparatus were developed by van Slyke and is known by his name. iv. Formol Reaction The H-atom of the Amino Group is substituted by the methylol group by treating with formaldehyde at room temperature. The formol reaction has the same analytical utility as the nitrous acid reaction. Aldehydes other than formaldehyde react in a similar manner. v. Reaction with Nitrosyl Chloride Nitrosyl chloride (or bromide) reacts with amino acids to form chloro (or bromo) acids, e.g., vi. Reaction with Hydriodic Acid When amino acid is heated with hydriodic acid at 200°C, the Amino Group is eliminated with the formation of a fatty acid. For example, alanine gives propionic acid when heated with HI at 200°C. vii. Oxidation to Keto Acid The deamination of amino acids to keto acids is of considerable biological significance. Chemically an amino acid can be converted to a keto acid by treating with hydrogen peroxide. In the biological systems, such oxidations are brought about by L -amino acid oxidases and D -amino acid oxidases...
eBook - ePub- J Fisher, J.R.P. Arnold, Julie Fisher, John Arnold(Authors)
- 2020(Publication Date)
- Taylor & Francis(Publisher)
...In combining two amino acids to form a dipeptide, an Amino Group reacts with a carboxyl group with the result that water is lost; this type of reaction is known as a condensation reaction (Figure 2). Figure 2 The formation of an amide or peptide bond results in the loss of a water molecule. The reactions of amines and carboxylic acid groups are dealt with in detail in Sections J3 and J4. It should be remembered that a number of side chains also have carboxylic acid or amine functions that may undergo reactions identical to those of the amine and carboxylic acid group, required to form the growing peptide chain. In addition, the amino acid cysteine has a free thiol (-SH) group in its side chain. This is readily oxidized to the disulfide, so care must be taken in handling this residue (Figure 3). Figure 3 Cysteine residues are readily oxidized (i.e. hydrogen removed) to their disulfide equivalent. In protein sequences S-S bridged cysteines are referred to as cystines to differentiate between them and residues with free thiol (-SH) groups. Amino acids can clearly display both acid and alkali properties. At neutral pH the carboxyl group is almost completely ionized (COO −) as is the Amino Group (NH 3 +). This positive and negatively charged system is referred to as a Zwitterion. As amino acids are ionized under neutral conditions they have physical properties similar to ionic compounds; that is, they are generally high melting point solids. Functional group protection In synthesizing a peptide or protein (either chemically or biochemically) it is important that the synthesis takes place in the correct direction. To illustrate, there are clearly three ways in which a glycine residue may be added to a lysine residue; an amide bond may be formed between the carboxyl of the glycine and the (a) α-Amino Group or the (b) ε-Amino Group of lysine, or between the (c) carboxyl of lysine and the glycine Amino Group...
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...
