Post on 17-Dec-2015
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Formation of acetyl-CoA from pyruvate
pyruvate
Acetyl-CoA + CO2 + NADH2
Pyruvatedehydrogenase
Acetyl-CoA + CO2 + H2Acetyl-CoA + formic acid
PyruvateFormate lyase
PyruvateFerredoxin
oxidoreductase
Anaerobically
Pyruvatedehydrogenase
1) Catalyze an oxidative decarboxylation.
2) It is found in aerobically grown Bacteria, mitocondria, but not in Archaea.
3) The product acetyl-CoA usually goes to the TCA cycle instead of to acetyl-P
HOOC-C-CH3 CH3CO-SCoA + CO2
O O
NAD NADH2
TCA cycle
HSCoA
PyruvateFormate lyase
1) Catalyze an oxidative decarboxylation.where the electrons remain in the carbonyl group.
2) The product acetyl-CoA usually goes to acetyl-P.
HOOC-C-CH3 + CoASH CH3CO-SCoA + CH2O2
O O
CH3CO-P + HSCoA
O
CH3COOH + ATP
Pi Phosphotransacetylase
Acetate kinase
ADP
Mg+
PyruvateFerredoxin
oxidoreductase
1) Catalyze an oxidative decarboxylation where ferredoxinis the Electron acceptor.
2) It is found typically in clostridia and sulfate reducing bacteria (SRB) and other anaerobes.
3) The product acetyl-CoA usually goes to acetyl-P.
HOOC-C-CH3 + CoASH CH3CO-SCoA + CO2
O O
Fd ox Fd red
2H+ 2H2
hydrogenase
CH3COOH + ATPAcetate kinase
ADPMg+
CH3CO-P + HSCoA
O
Pi
Phosphotransacetylase
How is acetyl-CoA made from Acetate?
It is typically made as follows
CH3COOH + ATPAcetate kinase
ADPMg+
CH3CO-P + HSCoA
O
Pi
Phosphotransacetylase
CH3CO-SCoA
O
acetylCoAsynthetase
or
INOUT
Carbon and energy
Lactic Acid Bacteria
Characteristics: Gram positive, carbohydrate users, proteolysis rare, nonmotile, non-spore forming
Strict fermentors, unable to synthesize cytochromes unless heme is
added. catalase negative oxidase negative
Nutritionally fastidious All make lactic acid (lactate) as predominant end
product
Lactic Acid Bacteria Types of fermentation Homofermentative: glucose to 2 lactic acids,
85-95% of glucose carbon in lactate Heterofermentative: glucose to 1 lactate, 1
ethanol, and 1 carbon dioxide, only 50% or less of glucose carbon in lactate.
Types of products will define the pathway used and ATP made.
Lactic Acid Bacteria
Types of organisms Streptococcus: homofermentative
Leuconostoc: heterofermentative
Pediococcus homofermentative
Lactobacillus; heterofermentative or homofermentative.
Lactic Acid Bacteria Streptococcus species: Enterococcus: gut dwellers Lactococcus
natural fermentations Lactic acid production: lowers pH,
preserves and precipitates proteins
Lactic acid bacteria Homofermentative pathway Uses Glycolytic pathway to make 2 pyruvates
from glucose Overview:
Activation-use 2 ATP Make ß-carbonyl C-C bond cleavage Oxidation/reduction Substrate-level phosphorylation
Glucose
Glucose-6-P
Homofermentative Pathway in Streptococci
ADPATP
Used 2 ATPMade 4 ATPNet ATP yield=2 ATP/glucose
Fructose-6-P
ADP
ATP
Fructose-1,6 bis P
Dihydroxyacetone-P 2 Glyceraldehyde-3-P
2 1,3-bisphosphoglycerate
2 3-phophoglycerate
2 2-phosphoglycerate
2 phosphoenolpyruvate
2 pyruvate
2 ADP
2 ATP
2 ADP2 ATP
2 NAD+
2 NADH
2 H2O
Dihydroxyacetone-Pconverted to glyceraldehyde-3-PPathway shows 2 G-3-P's afterthis step.
Reoxidation of NADH
2 pyruvate2 NADH
2 NAD+2 lactate
Lactate dehydrogenase
ATP
ADP
CH2
OH
OH OH OH
H HH
H
H
OC C C C CHO
Glycolytic Pathway for Glucose Metabolism
Glucose
Hexokinase or PTS systemATP
ADP
+
Glucose-6-P
Fructose-6-P
Fructose-1,6-bisP
Glyceraldehyde-3-P Dihydroxyacetone-P
G6P isomerase
Phosphofructo-kinase
Fructose-1,6-bis Paldolase
Triose isomeraseNow have 2 G3P's
CH2
OH
OH OH OH
H HH
H
H
OC C C C C=3OP O
=3OP O
H
CH2
OH
OH OH
H H
H O
C C C C CH2OH
=3OP O
H
CH2
OH
OH OH
H H
H O
C C C C CH2 PO3=
CH2
OH O
H H
C C=3OP O
OH
H O
C C CH2 PO3=H O
ATP
ADP
Glycolytic Pathway for Glucose Metabolism
Glyceraldehyde-3-P(Metabolism of only one G3P is shown)
=3OP O CH2
OH O
H H
C C
CH2
OH
OH
C C S-Enz=3OP O
CH2
OH
OH
C C=3OP O O-PO3
=
CH2
OH
OH
C C=3OP O OH
O-PO3=
HO-CH2
OH
C C OH
O-PO3=
CH2
O
C C OH
O
CH3
O
C C OH
{ }
NAD+
NADH
PO4=
H2O
ADP
ATP
1,3-bisphospho-glycerate
3-phosphoglycerate
2-phosphoglycerate
phosphoenolpyruvate
pyruvate
Triosephosphatedehydrogenase
Phosphoglyceratekinase
Phosphoglyceratemutase
Enolase
Pyruvatekinase
From the 3 and 4 carbonsof glucoseFrom the 1 and 6 carbons
of glucose
Mechanism of the isomeration reaction
H2CO PO3=
C
HCOH
HOCH
HCOH
H OH
OHC
O
H2CO PO3=
C
HCOH
HOCH
HCOH
H
H
C OH
H2CO PO3=
C
HCOH
HOCH
HCOH
O
HC OH
H
Glucose-6-P cis-enolateFructose-6-P
Isomerization Reaction:Creates an electron attracting keto group at the # 2 carbon
• H dissociates from C2• 2 electrons shift to form cis enediol• H from hydroxyl group dissociates• 2 electrons shift to form keto group.• Forces electrons in enol bond to shift to C1.
C-C bond cleavage: Aldolase Reaction
H dissociates from C4; 2 electrons shift to form cis enediolH from hydroxyl group (C4) dissociates2 electrons shift to form keto group.Forces electrons in enol bond to shift to C1.
H2CO PO3=
C O
H2CO PO3=
HCOH
HOCH
HC HO
CHOH
C O-
H2CO PO3=
H2CO PO3=
HCOH
CH O
+
C O
H2CO PO3=
C
H
OH
Mechanism of the aldolase reaction
Carbonyl betato Carbon with O
Enol formation
Dihydroxyacetone-P
Glyceraldehyde-3-P
Coenzymes (cofactors)/Vitamins Some are bound to enzyme
Apoenzyme + cofactor give holoenzyme Metal ion, organic cofactors
Some are soluble Act as co-substrate Pyruvate + NADH + H+ --> lactate + NAD+
Vitamins: Portion of cofactor that cell can’t make, must be in
diet “Vital amine”
N
C NH2
O
N
COOH
Vitamin Forms
Nicotinic acid(niacin) Nicotinamide
Vitamin forms: Niacin
Nutritional disease: pellagra
PO4
=in NADP+
NH2
N
C
O
NH2
O
OHOH
HH
H
CH2
H
O
OP
P
O
OHOH
HH
H
CH2O
O
HO
HO
O
N
NN
N
+
R
N
CC
CCC
+H
H
H
H
O
NH2C
H
H
R
N
CC
CCC
H H
H
O
NH2C
-2H
+2H
Oxidized Form Reduced Form
Nicotinamide Adenine Dinucleotide
NAD functions Function: oxidation reduction reaction,
accepts hydride anion (H-): one proton and two electrons
That’s why we write NADH + H +
Biosynthesis uses NADP+ most often Catabolism uses NAD+ most often.