apicomplexan biochemistry basics
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Apicomplexan Biochemistry Basics Toxoplasma
Good cell biology model Genome sequencing not completed Virtual pathways
Cryptosporidium The “strange one” Genome sequence completed Virtual pathways
Plasmodium Best biochemistry data Numerous studies over many years Genome sequencing completed!
Glycolysis - Plasmodium
Lactate
Pentose Pathway
Pyruvate
PEP
Glucose-6-P
Pyruvate Metabolism
Erythrocytic stage Glucose is major substrate
Infected RBC’s utilize 75%more glucose than uninfected
Lactate is major end product 85% of glucose lactate
High glycolytic rate Enzyme utilize ATP (not PPi) Overall 2 ATP produced for
every glucose utilized
Role of mitochondrion???
Pentose PhosphatePathway
Salvagepathway
Essential biosynthetic
pathwayShikimatepathway
Glycolytic intermediate isutilized (G-6-P)
Reducing equivalentsgenerated
Products utilized forNucleotide metabolism
Products utilized forshikimate pathway
Regenerates someglycolytic intermediates
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Shikimate Pathway
Important pathway that isabsent from animals! Folate synthesis Aromatic amino acid
synthesis Essential for apicomplexan
parasites Large body of data on
biochemistry Bacteria, fungi, plants
Glycolysis
PPP
FolateSynthesis
UbiquinoneSynthesis
TryptophanSynthesis
Mitochondrial Function Simplified View???
Historically thought to bequiescent
Few if any cristae Developmental changes
Asexual stages Single mitochondrion tubular
network Gametocytes
Multiple organelles Basics - Asexual stage
Cytosolic glycolysis Complete complement of TCA
cycle enzymes Electron transport subunits Alternative oxidase
Mito Oxidative Phosphorylation
Apicomplexans
Trypanosomatids
Cryptosporidium
Toxoplasma
Plasmodium
TrypanosomaBloodstream form
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Puzzle of Pyruvate Metabolism
Acetyl-CoA
Pyruvate Dehydrogenase Complex Multienzyme complex (PDC)
E1 - pyruvate dehydrogenase E2 - dihyrolipoyl transacteylase E3 - dihydrolipoyl dehydrogenase
Convert Pyruvate to Acetyl-CoA,generate reducing equivalents
Typically the regulated step committingto TCA cycle
PDC is absent from mitochondriaPDC is present in apicoplastE3 subunits present in mitochondria
Endocytosis of Host Cytoplasm
Pinocytosis Cytostome Endocytic pathway Food Vacuole
Hemoglobin digestion
• heme destabilizes and lysesmembranes• hydrolases released into
parasite cytoplasm• parasite dies
Heme β-hematin
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The Plasmodium Food Vacuole
hemoglobin
+heme globinfragments
small fragments(6-8 amino acids)
hemozoinATP
ADP
ATP
ADP
H+
Fe3+
Fe2+O2
H2O2
H2O + O2
-O2 •O2superoxidedismutase?
catalase?
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plasmepsin
falcipain
plasmepsin
falcilysin
Pfmdr-1?
aminoacids
A specialized lysosome - acidic compartment
Malaria pigmentMalaria pigment
The Power of Genomics Hugely difficult to isolate intact
apicoplasts in pure form. Why?
How do you study the function?
Virtual pathways!
Confirmation!!!!!
Delayed Death Phenotype Ciprofloxacin
inhibited apicoplast DNA replication(T. gondii)
Treatment resulted in: Loss of apicoplast DNA Cell growth inhibited after 1 round of
cell division
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Apicoplast functions - Simplified!
Apicoplast is an essential organelle - delayed death phenotype
Non-photosynthetic!
Transporters:Plant-like
1-deoxy-D-xylulose-5-phosphateDOXP pathway:
Bacteria, chloroplasts
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An Unusual DNA Polymerase
Fatty Acid Synthesis Iterative elongation of
acyl chains Growth of chain by 2 C
Type I (Eukaryotic) Multiple enzymatic
activities on a singlelarge multifunctionalprotein
Type II (Prokaryotic) Each activity is on a
separate polypeptide
Dr. Kim Paul
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Inhibition of Type II FAS
Initially thought: no FAS Type II - prokaryotic
Separate subunits ACC - acetyl CoA carboxylase
Aryloxyphenoxyproprionateherbicides (FOPS)
ACP - acyl carrier protein KAS - keto-acyl ACP synthase
Thiolactomycin Cerulenin
ENR - enoyl reductase Triclosan
The Good, the Bad, the Ugly
What purpose do Triclosan and the Copolymerserve?
Colgate Total is the only toothpaste to contain triclosanwith a copolymer.Triclosan is an effective antibacterial ingredient, whichis effective in controlling a wide range of bacteria.The copolymer is used in the formulation to prolongretention of triclosan on oral hard and soft tissues andin plaque.
Without the copolymer, triclosan would be rapidly lostfrom the mouth, reducing its clinical effect.
Bottom line: (numerous studies) Antibacterial ingredient triclosan degrades rapidly
when exposed to chlorinated tap water, producingpotentially toxic byproducts (chloroform).
The really uglyWhen flushed into water systems, and exposed toultra violet radiation, triclosan converts to a dioxin.The amount of dioxins created is small, however,it's an extremely toxic and stable chemical thatpersists in the environment and is eliminatedslowly from the body.
Sewage sludge - commonly used on farmer’s fields
Isoniazid
1st line anti-tuberculosisInhibits mycolic acid synthesis (mycobacterial cell wall)
Drug resistance is a big problem.Never use Isoniazid alone.
Mycolic acids consist of long-chainalpha-alkyl-beta-hydroxy fatty acids that are
produced by successive rounds of elongation catalyzed by a type II fatty acid synthase (FAS-II).
Apicoplast functions - Simplified!
Apicoplast is an essential organelle - delayed death phenotype
Non-photosynthetic!
Transporters:Plant-like
1-deoxy-D-xylulose-5-phosphateDOXP pathway:
Bacteria, chloroplasts
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