SSB End of Unit Review Eric Niederhoffer SIU-SOM

Submitted Questions Which enzymes are inhibited by elevated NADH versus which steps cause elevated NADH? Inhibited: Dehydrogenases Elevated: ADH, AlDH Specific inhibitory/activating substrate interactions with PFK1, PFK2 Inhibitory: ATP, citrate Activating: F6P, F26BP, F16BP, NH4+, AMP, Pi Why F16BP stimulates both PFK1 and PK? Feed-forward activation Significant and differentiating characteristics of metabolic diseases (examples given in RS) Physical symptoms, metabolites

Cellular Processing Oh my! Now what? EtOH CAT MEOS ADH P450 Peroxisome Cytosol ER CAT H2O2 H2O ADH NAD+ NADH MEOS NADP+ NADPH O2 P450 Pyrazole Aminotriazole Acetaldehyde Mitochondrion AlDH NAD+ NADH Disulfiram (antabuse) Chlorpropamide (diabetes) Acetate Extra-hepatic tissue

Pathway Perturbations Glc G6Pase F16BPase G6P GK Cytosol F6P F16BP PFK Protein Ala ALT OAA Asp AST PEP PEPCK OAA MDH NAD+ NADH Lactate LDH NAD+ Pyr PK Malate MDH NADH NADH NADH PC PDH Acetyl CoA FA β-Ox NADH Malate OAA MDH NAD+ Cit ICit NADH Malate Suc Fum Mitochondrion αKG IDH NAD+ S CoA αKGDH NAD+ NADH NADH

Regulation in Skeletal Muscle PKA AC cAMP ATP Ep AR Glc Glycolysis G6P PP ATP Citrate Acetyl-CoA Pyr F6P F16BP PEP Ca2+ PKa PFK-2 F26BP NH4+ AMP Pi Pi IMP AMP PFK-1 Glycogen Glycogenolysis b-Oxidation Ca2+ PDHP PDHK PDH Fatty acids PK PDH

Glycogen Storage Disease Type VII (Tarui Disease) Classic, infantile onset, Late onset Exercise intolerance, fatigue, myoglobinuria Phosphofructokinase Tetramer of three subunits (M, L, P) Muscle/heart/brain - M4; liver/kidneys - L4; erythrocytes - M4, L4, ML3, M2L2, M3L General symptoms of classic form Muscle weakness, pronounced following exercise Fixed limb weakness Muscle contractures Jaundice Joint pain Laboratory studies Increased serum creatine kinase levels No increase in lactic acid levels after exercise Bilirubin levels may increase Increased reticulocyte count and reticulocyte distribution width Myoglobinuria after exercise Ischemic forearm test - no lactate increase with ammonia increase

Pyruvate Dehydrogenase Complex Deficiency Neonatal, infantile, childhood onset Abnormal lactate buildup (mitochondrial disease) Pyruvate dehydrogenase complex E1 -  (thiamine dependent) and  subunits, 22 tetramer E2 - monomer (lipoate dependent) E3 - dimer (riboflavin dependent) common to KGDH and BCAKDH X protein - lipoate dependent Pyruvate dehydrogenase phosphatase Nonspecific symptoms (especially with stress, illness, high carbohydrate intake) Severe lethargy, poor feeding, tachypnea Key feature is gray matter degeneration with foci of necrosis and capillary proliferation in the brainstem (Leigh syndrome) Infants with less than 15% PDH activity generally die Developmental nonspecific signs Mental delays Psychomotor delays Growth retardation Laboratory studies High blood and cerebrospinal fluid lactate and pyruvate levels Elevated serum and urine alanine levels If E2 deficient, elevated serum AAs and hyperammonemia If E3 deficient, elevated BCAA in serum, KG in serum and urine

Maple Syrup Urine Disease (Branched-Chain -Ketoaciduria) Classic (early) and late onset (5 clinical phenotypes; classic, intermediate, intermittent, thiamine-responsive, and E3-deficient) Encephalopathy and progressive neurodegeneration Branched-chain -ketoacid dehydrogenase complex E1 -  (thiamine dependent) and  subunits, 22 tetramer E2 - monomer (lipoate dependent) E3 - dimer (riboflavin dependent) common to KGDH and PDH BCKD kinase BCKD phosphatase Initial symptoms Poor feeding, vomiting, poor weight gain, and increasing lethargy Neurological signs Alternating muscular hypotonia and hypertonia, dystonia, seizures, encephalopathy Laboratory studies Elevated BCAA in serum Presence of alloisoleucine in serum Presence of -HIV, lactate, pyruvate, and KG in urine Treatment Restriction of BCAA Supplementation with thiamine