The role of glucosamine-6-phosphate deaminase at the early stages of Aspergillus niger growth in a high-citric-acid-yielding medium
| Autor: | Tina Šolar, Matic Legiša, Janja Turšič |
|---|---|
| Rok vydání: | 2008 |
| Předmět: |
Applied Microbiology and Biotechnology
Citric Acid Fungal Proteins chemistry.chemical_compound Glucosamine Ammonium Aldose-Ketose Isomerases chemistry.chemical_classification biology Aspergillus niger Fructosephosphates General Medicine biology.organism_classification Culture Media Quaternary Ammonium Compounds Kinetics Enzyme chemistry Biochemistry Aminosugar Fermentation Citric acid Flux (metabolism) Biotechnology |
| Zdroj: | Applied Microbiology and Biotechnology. 78:613-619 |
| ISSN: | 1432-0614 0175-7598 |
| Popis: | Glucosamine-6-phosphate (GlcN6P) deaminase seems to be the main enzyme in Aspergillus niger cells responsible for rapid glucosamine accumulation during the early stages of growth in a high-citric-acid-yielding medium. By determining basic kinetic parameters on the isolated enzyme, a high affinity toward fructose-6-phosphate (Fru6P) was measured, while in the reverse direction the K(m) value for glucosamine-6-phosphate was lower than deaminases from other organisms measured so far. The enzyme characteristics of GlcN6P deaminase suggest it must compete with 6-phosphofructo-1-kinase (PFK1) for the common substrate-Fru6P in A. niger cells. Glucosamine accumulation seems therefore to remove an intermediate from the glycolytic flux, a situation which is reflected in slower citric acid accumulation and a specific growth rate after the germination of spores. When ammonium ions are depleted from the medium, one of the substrates for GlcN6P deaminase becomes limiting and Fru6P can be catabolised by PFK1 which enhances glycolytic flux. Other enzymatic features of GlcN6P deaminase such as pH optima for both aminating and deaminating reactions might play a significant role in rapid glucosamine accumulation during the early phase of fermentation and a slow consumption of aminosugar during the citric-acid-producing phase. |
| Databáze: | OpenAIRE |
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