Aspergillus fumigatus catalytic glucokinase and hexokinase: expression analysis and importance for germination, growth, and conidiation.
Fungi contain several hexokinases, which are involved either in sugar phosphorylation or in carbon source sensing. Glucose and fructose phosphorylations appear to rely exclusively on glucokinase and hexokinase. Here, we characterized the catalytic glucokinase and hexokinase from the opportunistic human pathogen Aspergillus fumigatus and showed that both enzymes display different biochemical properties and play different roles during growth and development. Glucokinase efficiently activates glucose and mannose but activates fructose only to a minor extent. Hexokinase showed a high efficiency for fructose activation but also activated glucose and mannose. Transcript and activity determinations revealed high levels of glucokinase in resting conidia, whereas hexokinase was associated mainly with the mycelium. Consequentially, a glucokinase mutant showed delayed germination at low glucose concentrations, whereas colony growth was not overly affected. The deletion of hexokinase had only a minor impact on germination but reduced colony growth, especially on sugar-containing media. Transcript determinations from infected mouse lungs revealed the expression of both genes, indicating a contribution to virulence. Interestingly, a double-deletion mutant showed impaired growth not only on sugars but also on nonfermentable nutrients, and growth on gluconeogenic carbon sources was strongly suppressed in the presence of glucose. Furthermore, the glkA hxkA deletion affected cell wall integrity, implying that both enzymes contribute to the cell wall composition. Additionally, the absence of either enzyme deregulated carbon catabolite repression since mutants displayed an induction of isocitrate lyase activity during growth on glucose-ethanol medium. Therefore, both enzymes seem to be required for balancing carbon flux in A. fumigatus and are indispensable for growth under all nutritional conditions.
Fleck
Christian B
CB
Leibniz Institute for Natural Product Research and Infection Biology, Hans Knoell Institute, Microbial Biochemistry and Physiology, Beutenbergstr. 11a, 07745 Jena, Germany.
Brock
Matthias
M
D000818:Animals; D001228:Aspergillosis / Q000382:microbiology; D001232:Aspergillus fumigatus / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development*; D055162:Biocatalysis / Q000187:drug effects; D002244:Carbon / Q000494:pharmacology; D002473:Cell Wall / Q000187:drug effects / Q000201:enzymology; D017353:Gene Deletion; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D015966:Gene Expression Regulation, Fungal / Q000187:drug effects; D005941:Glucokinase / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000302:isolation & purification; D006593:Hexokinase / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000302:isolation & purification; D006801:Humans; D008168:Lung / Q000201:enzymology / Q000382:microbiology; D051379:Mice; D025282:Mycelium / Q000201:enzymology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013172:Spores, Fungal / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D013379:Substrate Specificity / Q000187:drug effects; D013403:Sugar Phosphates / Q000494:pharmacology; D014199:Trehalose / Q000031:analogs & derivatives / Q000494:pharmacology
D012333:RNA, Messenger; D013403:Sugar Phosphates; C082722:trehalose-6-phosphate; D002244:Carbon; D014199:Trehalose; D006593:Hexokinase; D005941:Glucokinase
Microbiol Mol Biol Rev. 1998 Jun;62(2):334-61
9618445
FEMS Microbiol Lett. 1996 Jun 1;139(2-3):223-28
8674991
Int Rev Cell Mol Biol. 2008;269:111-50
18779058
Biotechnology. 1992;23:43-68
1504607
J Biol Chem. 2006 Mar 31;281(13):8339-46
16418173
Fungal Genet Biol. 2008 May;45(5):618-27
17981060
Microbiology (Reading). 2007 Aug;153(Pt 8):2791-2802
17660443
Fungal Genet Biol. 2009 Mar;46 Suppl 1:S19-S44
19610199
Microb Biotechnol. 2009 Mar;2(2):132-3
21261892
Prog Nucleic Acid Res Mol Biol. 2001;69:149-204
11550794
J Biol Chem. 2003 Apr 4;278(14):11849-57
12519784
Genetics. 2000 Jan;154(1):121-32
10628974
Methods. 2001 Dec;25(4):402-8
11846609
Clin Chest Med. 2009 Jun;30(2):295-306, vii
19375636
Microbiology (Reading). 2005 Jul;151(Pt 7):2209-2221
16000711
Fungal Genet Biol. 2006 Jul;43(7):476-89
16603391
Microbiology (Reading). 2001 Jul;147(Pt 7):1851-1862
11429462
J Biotechnol. 2002 Jan 18;92(3):279-85
11689252
Fungal Genet Biol. 2006 Aug;43(8):593-603
16698295
Eukaryot Cell. 2006 May;5(5):816-24
16682459
Microbiology (Reading). 2003 Aug;149(Pt 8):2129-2136
12904552
Microbiology (Reading). 2007 Jun;153(Pt 6):1963-1973
17526853
EMBO J. 2007 Jul 11;26(13):3157-68
17568774
Genetics. 2000 Dec;156(4):1559-71
11102357
Mol Genet Genomics. 2007 May;277(5):519-32
17226029
FEMS Yeast Res. 2008 Feb;8(1):155-64
17662056
Nucleic Acids Res. 2001 May 1;29(9):e45
11328886
Fungal Genet Biol. 2004 Feb;41(2):148-56
14732261
Mol Microbiol. 1997 Apr;24(1):203-16
9140977
Mol Microbiol. 1999 May;32(3):471-83
10320571
Eur J Biochem. 1996 Sep 15;240(3):518-25
8856049
Appl Environ Microbiol. 2008 Nov;74(22):7023-35
18820063
Nature. 2007 Sep 6;449(7158):54-61
17805289
Eur J Biochem. 1998 Nov 15;258(1):223-32
9851713
J Gen Microbiol. 1963 Apr;31:45-58
13974284
Curr Genet. 1998 May;33(5):378-85
9618589
BMC Microbiol. 2010 Apr 08;10:105
20377900
Fungal Genet Biol. 2007 Mar;44(3):219-30
16990036
Microbes Infect. 2009 Oct;11(12):919-27
19615460
Infect Immun. 2003 Feb;71(2):891-903
12540571
Contrib Microbiol. 2009;16:65-87
19494579
Cell Microbiol. 2008 Jan;10(1):134-48
17973657
Mol Microbiol. 2008 May;68(3):642-56
18331473
Crit Care Med. 2008 Aug;36(8):2249-55
18664780
Arch Microbiol. 2004 Jan;181(1):35-44
14624333
FEMS Microbiol Lett. 1997 Jun 15;151(2):103-14
9228741
J Bacteriol. 1969 Dec;100(3):1198-203
5361211
Microbiology (Reading). 2009 Oct;155(Pt 10):3281-3293
19574302