β-lactam

Examples of β-lactam in the following topics:

• Beta-Lactam Antibiotics: Penicillins and Cephalosporins

  • The β-lactam ring is part of the core structure of several antibiotic families.
  • A β-lactam (beta-lactam) ring, is a four-membered lactam .
  • The simplest β-lactam possible is 2-azetidinone.
  • The β-lactam ring is part of the core structure of several antibiotic families, the principal ones being the penicillins, cephalosporins, carbapenems, and monobactams, which are, therefore, also called β-lactam antibiotics.
  • Together with cephamycins, they constitute a subgroup of β-lactam antibiotics called cephems.

• Inhibiting Cell Wall Synthesis

  • β-Lactam (beta-lactam) and glycopeptide antibiotics work by inhibiting or interfering with cell wall synthesis of the target bacteria.
  • The first class of antimicrobial drugs that interfere with cell wall synthesis are the β-Lactam antibiotics (beta-lactam antibiotics), consisting of all antibiotic agents that contains a β-lactam nucleus in their molecular structures.
  • PBPs vary in their affinity for binding penicillin or other β-lactam antibiotics.
  • Bacteria often develop resistance to β-lactam antibiotics by synthesizing a β-lactamase, an enzyme that attacks the β-lactam ring.
  • To overcome this resistance, β-lactam antibiotics are often given with β-lactamase inhibitors such as clavulanic acid.

• Naturally Occurring Antimicrobial Drugs: Antibiotics

  • There are mainly two classes of antimicrobial drugs: those obtained from natural sources (i.e. beta-lactam) antibiotic (such as penicillins, cephalosporins) or protein synthesis inhibitors (such as aminoglycosides, macrolides, tetracyclines, chloramphenicol, polypeptides); and synthetic agents.
  • A β-lactam (beta-lactam) ring is a four-membered lactam.
  • A lactam is a cyclic amide.
  • It is named as such, because the nitrogen atom is attached to the β-carbon relative to the carbonyl.
  • The simplest β-lactam possible is 2-azetidinone.

• Antibiotic Classifications

  • Examples include the Beta-lactam antibiotics (penicillin derivatives (penams) ), cephalosporins (cephems), monobactams, and carbapenems) and vancomycin.
  • Penicillin and most other β-lactam antibiotics act by inhibiting penicillin-binding proteins, which normally catalyze cross-linking of bacterial cell walls.

• Lipid Metabolism

  • Biological lipids, which are broken down and utilized though β-oxidation, represent a potent energy source.
  • Although not stated explicitly, the "Organic Acid Metabolism" atom in this module introduces the concept of lipid metabolism by describing the process of fatty acid metabolism through β-oxidation.
  • The metabolic process by which fatty acids and their lipidic derivatives are broken down is called β-oxidation.
  • β-oxidation can be broken down into a series of discrete steps:
  • Oxidation: The initial step of β-oxidation is catalyzed by acyl-CoA dehydrogenase, which oxidizes the fatty acyl-CoA molecule to yield enoyl-CoA.

• Organic Acid Metabolism

  • This process requires the β-oxidation pathway, a cyclic process that catalyzes the sequential shortening of fatty acid acyl chains to the final product, acetyl-CoA.
  • The fatty acid chain that is left over after the thiolation step can then reenter the β-oxidation pathway, which can cycle until the fatty acid has been completely reduced to acetyl-CoA.
  • Free fatty acids are broken down to acetyl-CoA by dedicated enzymes in the β-oxidation pathway.

• Peptidoglycan Synthesis and Cell Division

  • Some Archaea have a similar layer of pseudopeptidoglycan or pseudomurein, where the sugar residues are β-(1,3) linked N-acetylglucosamine and N-acetyltalosaminuronic acid.
  • The sugar component consists of alternating residues of β-(1,4) linked N-acetylglucosamine and N-acetylmuramic acid.
  • Some Archaea have a similar layer of pseudopeptidoglycan or pseudomurein, where the sugar residues are β-(1,3) linked N-acetylglucosamine and N-acetyltalosaminuronic acid.

• Cell-Mediated Autoimmune Reactions

  • This requirement of a T cell can be bypassed in rare instances, such as infection by organisms producing super-antigens, which are capable of initiating polyclonal activation of B cells, or even of T cells, by directly binding to the β-subunit of T cell receptors in a non-specific fashion.
  • The α and β chains are encoded by HLA-DQA1 and HLA-DQB1, respectively.
  • Both the α-chain and β-chain vary greatly.
  • A person often produces two α-chain and two β-chain variants and thus four DQ isoforms.

• Verrucomicrobia

  • rpoB is the gene that encodes the β subunit of bacterial RNA polymerase.

• Diverse Cell Forms of Methanogens

  • These differences makes these archaea resistant to the enzyme, lysozyme, which only breaks down β (1,4) sugar linkages like those found in peptidoglycan.