Amino acids derivetives
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Amino acids derivetives

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  • Many metabolites and pharmaceuticals are excreted as water-soluble glycine conjugates. The capacity of the liver to convert benzoate to hippuric acid formerly was used to assess liver function. <br />
  • Spermidine and spermine function in diverse physiologic processes that share as a common thread a close relationship to cell proliferation and growth. <br /> The fact that they are polycations allows these compounds to bind to DNA and RNA and they are involved in packaging of DNA in bacteriophages. <br />
  • Addition of inhibitors of ornithine decarboxylase, the enzyme that catalyzes the initial reaction in polyamine biosynthesis, triggers overproduction of ornithine decarboxylase. (hence, the machinary that makes the protein is regulated tightly in order that a supply of the precursors to spermidine and spermine is always available. <br />
  • ALA synthase is the rate-controlling enzyme in porphyrin biosynthesis. ALA dehdratase is sensitive to inhibition to lead, as can occur in lead poisoning. <br />

Amino acids derivetives Amino acids derivetives Presentation Transcript

  • M.Prasad Naidu MSc Medical Biochemistry, Ph.D,.
  • Heme purines pyrimidines hormones neurotransmitters biologically active peptides
  • Derived from beta-alanine and histidine Anserine is formed by methylation of carnosine by S-adenosylmethione (beta-alanine is derived from cytosine) Carnosine and anserine occur in muscle and activate myosin ATPase activity (myosin is the chief enyzme involved in contraction of muscle) Homocarnosine occurs in the brain. Homocarnosinosis is an extremely rare disorder due to carnosinase deficiency. It is associated with mental retardation Decarboxylation of histidine forms histamine. Other compounds arising from histidine are shown here
  • Spermidine and spermine function in diverse physiologic processes that share as a common thread a close relationship to cell proliferation and growth. The fact that they are polycations allows these compounds to bind to DNA and RNA and they are involved in packaging of DNA in bacteriophages.
  • Addition of inhibitors of ornithine decarboxylase, the enzyme that catalyzes the initial reaction in polyamine biosynthesis, triggers overproduction of ornithine decarboxylase. (hence, the machinery that makes the protein is regulated tightly in order that a supply of the precursors to spermidine and spermine is always available). Ornithine decarboxylase has a half-life of 10 minutes.
  • Melatonin regulates circadian rhythms Tyrosine hydroxylase tryptophan Serotonin is a potent vasoconstrictor and stimulator of smooth muscle contraction Inhibition of MAO by iproniazid increases effects of serotonin
  • Melanin polymers contain both eumelanin and pheomelanin in varying amounts. Albinism accompanies defective melanin biosynthesis. Tyrosine hydroxylase-negative albinos lack all visual pigment
  • Creatine is a high-energy storage compound in muscle. ATP is made from creatine phosphate by creatine kinase
  • Porphyrias are a group of diseases caused by abnormalities in the pathway of biosynthesis of various porphyrins. Examples of important porphyrins in nature are the iron porphyrins such as the heme of hemoglobin, and the magnesium porphyrin in chlorophyll.
  • Usually, type III is formed but in certain porphyrias, the type I isomers are formed in excess. These compounds are not conjugated due to the methylene groups. Oxidation is catalyzed by light leading to formation of the colored porphyrins.
  • Porphyrins have a very strong absorbance due to extended conjugation of double bonds. Porphyrins are used in cancer phototherapy. Tumors often take up more porphyrins than normal tissue. Lasers will excite the porphyrin to a high energy intermediate that breaks down and resleases cytotoxic agents that kill the tumor. Accumulation of porphyrinogens can cause sensitivity to light leading to skin damages
  • Mutations in in enzymes 2- 8 cause the porphyrias. Regulation of heme synthesis occurs at ALA synthase by a repression-derepression mechanism mediated by heme. The dotted lines indicate the negative regulation by repression.