Intermediary metabolism Vladimíra Kvasnicová

Intermediary metabolism relationships (saccharides, lipids, proteins) after feeding (energy intake in a diet) oxidation → CO2, H2O, urea + ATP formation of stores → glycogen, TAG Urea

Glycogen reducing end nonreducing end The figures were found (May 2007) at http://www.wellesley.edu/Chemistry/chem227/sugars/oligo/glycogen.jpg http://students.ou.edu/R/Ben.A.Rodriguez-1/glycogen.gif, http://fig.cox.miami.edu/~cmallery/255/255chem/mcb2.10.triacylglycerol.jpg

Intermediary metabolism relationships (saccharides, lipids, proteins) during fasting use of energy stores glycogen → glucose TAG → fatty acids formation of new energy substrates gluconeogenesis (glycerol, muscle proteins) ketogenesis (storage TAG → FFA → ketone bodies)

The figure was adopted from Devlin, T. M The figure was adopted from Devlin, T. M. (editor): Textbook of Biochemistry with Clinical Correlations, 4th ed. Wiley‑Liss, Inc., New York, 1997. ISBN 0‑471‑15451‑2

The figure was adopted from Devlin, T. M The figure was adopted from Devlin, T. M. (editor): Textbook of Biochemistry with Clinical Correlations, 4th ed. Wiley‑Liss, Inc., New York, 1997. ISBN 0‑471‑15451‑2

Principal metabolic pathways of the intermediary metabolism: glycogenolysis glycolysis lipolysis -oxidation ketone bodies degr. proteolysis degradation of AA glycogenesis gluconeogenesis lipogenesis synthesis of FA ketogenesis proteosynthesis urea synthesis CITRATE CYCLE, RESPIRATORY CHAIN

acetyl-Co A pyruvate NADH Major intermediates acetyl-Co A pyruvate NADH

acetyl-CoA pyruvate (PDH) – i.e. from glucose amino acids (degrad.) – from proteins fatty acids (-oxidation) – from TAG ketone bodies (degrad.) – from FA acetyl-CoA citrate cycle, RCH → CO2, H2O, ATP synthesis of FA synthesis of ketone bodies synthesis of cholesterol synthesis of glucose !!!

degradation of some amino acids aerobic glycolysis oxidation of lactate (LD) degradation of some amino acids pyruvate acetyl-CoA (PDH) lactate (lactate dehydrogenase) alanine (alanine aminotransferase) oxaloacetate (pyruvate carboxylase) glucose (gluconeogenesis)

respiratory chain → reoxidation to NAD+ ! OXYGEN SUPPLY IS NECESSARY! aerobic glycolysis PDH reaction -oxidation citrate cycle oxidation of ethanol NADH respiratory chain → reoxidation to NAD+ energy storage in ATP ! OXYGEN SUPPLY IS NECESSARY!

NADH pyruvate → lactate aerobic glycolysis PDH reaction -oxidation citrate cycle oxidation of ethanol NADH pyruvate → lactate respiratory chain → reoxidation to NAD+ energy storage in ATP ! OXYGEN SUPPLY IS NECESSARY!

The most important is to answer the questions: WHERE? WHEN? HOW? compartmentalization of the pathways starve-feed cycle regulation of the processes

Compartmentalization of mtb pathways The figure is found at http://fig.cox.miami.edu/~cmallery/150/proceuc/c7x7metazoan.jpg (May 2007)

Cytoplasm glycolysis gluconeogenesis (from oxaloacetate or glycerol) metabolism of glycogen pentose cycle synthesis of fatty acids synthesis of nonessential amino acids transamination reactions synthesis of urea (a part; only in the liver!) synthesis of heme (a part) metabolism of purine and pyrimidine nucleotides

Mitochondrion pyruvate dehydrogenase complex (PDH) initiation of gluconeogenesis -oxidation of fatty acids synthesis of ketone bodies (only in the liver!) oxidation deamination of glutamate transamination reactions citrate cycle respiratory chain (inner mitochondrial membrane) aerobic phosphorylation (inner mitoch. membrane) synthesis of heme (a part) synthesis of urea (a part)

Endoplasmic Reticulum Smooth ER synthesis of triacylglycerols and phospholipids elongation and desaturation of fatty acids synthesis of steroids biotransformation of xenobiotics glucose-6-phosphatase Rough ER proteosynthesis (translation and posttranslational modifications)

Golgi Apparatus Nucleus posttranslational modification of proteins protein sorting export of proteins (formation of vesicules) Ribosomes proteosynthesis Nucleus replication and transcription of DNA synthesis of RNA

Lysosomes Peroxisomes hydrolysis of proteins, saccharides, lipids and nucleic acids Peroxisomes oxidative reactions involving O2 use of hydrogen peroxide degradation of long chain FA (from C20)

Starve-feed cycle relationships of the metabolic pathways under various conditions cooperation of various tissues see also http://www2.eur.nl/fgg/ow/coo/bioch/#english (Metabolic Interrelationships)

1) Well-fed state The figure was adopted from Devlin, T. M. (editor): Textbook of Biochemistry with Clinical Correlations, 4th ed. Wiley‑Liss, Inc., New York, 1997. ISBN 0‑471‑15451‑2

2) Early fasting state The figure was adopted from Devlin, T. M. (editor): Textbook of Biochemistry with Clinical Correlations, 4th ed. Wiley‑Liss, Inc., New York, 1997. ISBN 0‑471‑15451‑2

3) Fasting state The figure was adopted from Devlin, T. M. (editor): Textbook of Biochemistry with Clinical Correlations, 4th ed. Wiley‑Liss, Inc., New York, 1997. ISBN 0‑471‑15451‑2

4) Early refed state The figure was adopted from Devlin, T. M. (editor): Textbook of Biochemistry with Clinical Correlations, 4th ed. Wiley‑Liss, Inc., New York, 1997. ISBN 0‑471‑15451‑2

The figure was adopted from Devlin, T. M The figure was adopted from Devlin, T. M. (editor): Textbook of Biochemistry with Clinical Correlations, 4th ed. Wiley‑Liss, Inc., New York, 1997. ISBN 0‑471‑15451‑2

Changes of liver glycogen content The figure was adopted from Devlin, T. M. (editor): Textbook of Biochemistry with Clinical Correlations, 4th ed. Wiley‑Liss, Inc., New York, 1997. ISBN 0‑471‑15451‑2

WELL-FED STATE FASTING STATE hormones  insulin  glucagon, adrenaline, cortisol response of the body  glycemia  lipogenesis  proteosynthesis  glycemia  lipolysis  ketogenesis  proteolysis

WELL-FED STATE FASTING STATE hormones  insulin  glucagon, adrenaline, cortisol response of the body  glycemia  lipogenesis  proteosynthesis  glycemia  lipolysis  ketogenesis  proteolysis source of glucose from food from stores (glycogen) gluconeogenesis fate of glucose glycolysis formation of stores

WELL-FED STATE FASTING STATE source of fatty acids from food TAG from storage TAG fate of fatty acids -oxidation synthesis of TAG  -oxidation ketogenesis

WELL-FED STATE FASTING STATE source of fatty acids from food TAG from storage TAG fate of fatty acids -oxidation synthesis of TAG  -oxidation ketogenesis source of amino acids from food from muscle proteins fate of amino acids proteosynthesis oxidation lipogenesis gluconeogenesis

Metabolism of ammonia - the importance of glutamine - synthesis of nucleotides ( nucleic acids) detoxification of amino N (-NH2 transport) synthesis of citrulline (used in urea cycle):  intake of proteins in a diet (fed state) or  degradation of body proteins (starvation)  concentration of glutamine

=  detoxification of NH3 from degrad. of prot. enterocyte: Gln  citrulline  blood  kidneys kidneys: citrulline  Arg  blood  liver liver: Arg  urea + ornithine ornithine → increased velocity of the UREA CYCLE =  detoxification of NH3 from degrad. of prot.

General Principles of Regulation catabolic / anabolic processes last step of each regulation mechanism: change of a concentration of an active enzyme (= regulatory or key enzyme) regulatory enzymes often allosteric enzymes catalyze higly exergonic reactions (irreverzible) low concentration within a cell

I. Regulation on the organism level signal transmission among cells (signal substances) signal transsduction through the cell membrane influence of enzyme activity: induction of a gene expression interconversion of existing enzymes (phosphorylation / dephosphorylation)

II. Regulation on the cell level compartmentalization of mtb pathways change of enzyme concentration (on the level of synthesis of new enzyme ) change of enzyme activity (an existing enzyme is activated or inactivated)

1. Compartmentalization of mtb patways transport processes between compartments various enzyme distribution various distribution of substrates and products ( transport) transport of coenzymes subsequent processes are close to each other

2. Synthesis of new enzyme molecules: induction by substrate or repression by product (on the level of transcription) examples: xenobiotics  induction of cyt P450 heme  repression of delta-aminolevulate synthase

3. Change of activity of an existing enzyme in relation to an enzyme kinetics concentration of substrates ( Km) availability of coenzymes consumption of products pH changes substrate specificity - different Km

3. Change of activity of an existing enzyme activation or inactivation of the enzyme covalent modification of the enzymes interconversion: phosphorylation/dephosphorylation) cleavage of an precursore (proenzyme, zymogen) modulation of activity by modulators (ligands): feed back inhibition cross regulation feed forward activation

Phosphorylation / dephosphorylation some enzymes are active in a phosphorylated form, some are inactive phosphorylation: protein kinases macroergic phosphate as a donor of the phosphate (ATP!) dephosphorylation protein phosphatase inorganic phosphate is the product!

Reversible covalent modification: phosphorylation by a protein kinase dephosphorylation by a protein phosphatase B) phosphorylated enzyme is either active or inactive (different enzymes are influenced differently) The figure is found at: http://stallion.abac.peachnet.edu/sm/kmccrae/BIOL2050/Ch1-13/JpegArt1-13/05jpeg/05_jpeg_HTML/index.htm (December 2006)

Modulators of enzyme activity (activators, inhibitors) isosteric modulation: competitive inhibition allosteric modulation: change of Km or Vmax T-form (less active) or R-form (more active) important modulators: ATP / ADP