A hydrogenosome with pyruvate formate-lyase: anaerobic chytrid fungi use an alternative route for pyruvate catabolism.
The chytrid fungi Piromyces sp. E2 and Neocallimastix sp. L2 are obligatory amitochondriate anaerobes that possess hydrogenosomes. Hydrogenosomes are highly specialized organelles engaged in anaerobic carbon metabolism; they generate molecular hydrogen and ATP. Here, we show for the first time that chytrid hydrogenosomes use pyruvate formate-lyase (PFL) and not pyruvate:ferredoxin oxidoreductase (PFO) for pyruvate catabolism, unlike all other hydrogenosomes studied to date. Chytrid PFLs are encoded by a multigene family and are abundantly expressed in Piromyces sp. E2 and Neocallimastix sp. L2. Western blotting after cellular fractionation, proteinase K protection assays and determinations of enzyme activities reveal that PFL is present in the hydrogenosomes of Piromyces sp. E2. The main route of the hydrogenosomal carbon metabolism involves PFL; the formation of equimolar amounts of formate and acetate by isolated hydrogenosomes excludes a significant contribution by PFO. Our data support the assumption that chytrid hydrogenosomes are unique and argue for a polyphyletic origin of these organelles.
Akhmanova
A
A
Department of Microbiology and Evolutionary Biology, Faculty of Science, University of Nijmegen, Toernooiveld, 6525 ED Nijmegen, The Netherlands.
Voncken
F G
FG
Hosea
K M
KM
Harhangi
H
H
Keltjens
J T
JT
op den Camp
H J
HJ
Vogels
G D
GD
Hackstein
J H
JH
D000123:Acetyltransferases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000693:Anaerobiosis; D001483:Base Sequence; D015152:Blotting, Northern; D015153:Blotting, Western; D018076:DNA, Complementary; D004271:DNA, Fungal; D019286:Endopeptidase K / Q000378:metabolism; D015723:Gene Library; D005800:Genes, Fungal; D006859:Hydrogen / Q000378:metabolism*; D008928:Mitochondria / Q000201:enzymology; D008969:Molecular Sequence Data; D005810:Multigene Family; D015388:Organelles / Q000201:enzymology*; D010802:Phylogeny; D020089:Piromyces / Q000201:enzymology* / Q000235:genetics; D019289:Pyruvic Acid / Q000378:metabolism*; D016415:Sequence Alignment
D018076:DNA, Complementary; D004271:DNA, Fungal; D006859:Hydrogen; D019289:Pyruvic Acid; D000123:Acetyltransferases; C022560:formate C-acetyltransferase; D019286:Endopeptidase K