Yeast hexokinase has been poorly characterized in regard with its stability. In the present study, various spectroscopic techniques were employed to investigate thermal stability of the monomeric form of yeast hexokinase B (YHB). The enzyme underwent a conformational transition with a T(m) of about 41.9 degrees C. The structural transition proved to be significantly reversible below 55 degrees C and irreversible at higher temperatures. Thermoinactivation studies revealed that enzymatic activity diminished significantly at high temperatures, with greater loss of activity observed above 55 degrees C. Release of ammonia upon deamidation of YHB obeyed a similar temperature-dependence pattern. Dynamic light scattering and size exclusion-HPLC indicated formation of stable aggregates. Taking various findings on the influence of osmolytes and chaperone-like agents on YHB thermal denaturation together, it is proposed that the purely conformational transition of YHB is reversible, and irreversibility is due to aggregation, as a major cause. Deamidation of a critical Asn or Gln residue(s) may also play an important role. Study holds ProTherm entries: 25611, 25612, 25613, 25614, 25615, 25616 Extra Details: Yeast hexokinase B; Thermoinactivation; Aggregation; Deamidation; Size exclusion-HPLC
Submitter: Connie Wang
Submission Date: April 24, 2018, 8:55 p.m.
|Number of data points||6|
|Proteins||Hexokinase-2 ; Hexokinase-2|
|Assays/Quantities/Protocols||Experimental Assay: Tm details:Additives 1.5M sorbitol ; Experimental Assay: Tm details:Additives , prot_conc:0.15 mg/mL ; Experimental Assay: Tm details:Additives|
|Libraries||Mutations for sequence MVHLGPKKPQARKGSMADVPKELMQQIENFEKIFTVPTETLQAVTKHFISELEKGLSKKGGNIPMIPGWVMDFPTGKESGDFLAIDLGGTNLRVVLVKLGGDRTFDTTQSKYRLPDAMRTTQNPDELWEFIADSLKAFIDEQFPQGISEPIPLGFTFSFPASQNKINEGILQRWTKGFDIPNIENHDVVPMLQKQITKRNIPIEVVALINDTTGTLVASYYTDPETKMGVIFGTGVNGAYYDVCSDIEKLQGKLSDDIPPSAPMAINCEYGSFDNEHVVLPRTKYDITIDEESPRPGQQTFEKMSSGYYLGEILRLALMDMYKQGFIFKNQDLSKFDKPFVMDTSYPARIEEDPFENLEDTDDLFQNEFGINTTVQERKLIRRLSELIGARAARLSVCGIAAICQKRGYKTGHIAADGSVYNRYPGFKEKAANALKDIYGWTQTSLDDYPIKIVPAEDGSGAGAAVIAALAQKRIAEGKSVGIIGA|