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PIRUVAT KINASE

PIRUVAT KINASE. KELOMPOK IV Eka Susilawati (10506106) Sukmawati Ayu (10507032) Martalia Wahyu (10507034) Hasan Ramdan (10507056) Tiara Pelangi A (10507066) Sri Aryani (10507076).

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PIRUVAT KINASE

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  1. PIRUVAT KINASE KELOMPOK IV EkaSusilawati (10506106) SukmawatiAyu (10507032) MartaliaWahyu (10507034) HasanRamdan (10507056) Tiara Pelangi A (10507066) Sri Aryani (10507076)

  2. Three Glycolysis reactions have such a large negative DG that they are essentially irreversible. • Hexokinase(or Glucokinase) • Phosphofructokinase • PyruvateKinase. PyruvateKinase (last step of Glycolysis) catalyzes: phosphoenolpyruvate+ ADP pyruvate + ATP

  3. PiruvatKinaseadalahenzim yang mengkatalisislangkahirreversibelketigapadaglikolisis • PiruvatKinasemenghasilkan ATP danPiruvat • Bilamuatanenergitinggi , ATP secaraallosterikmenginhibisiPiruvatKinaseuntukmemperlambatglikolisis

  4. PengontrolanaktivitaskatalitikPiruvatKinase PiruvatKinaseterfosforilasi (kurangaktif) ADP H2O - Kadar glukosadarahmerah + PI ATP PiruvatKinaseterdesfosforilasi (lebihaktif) Fosfoenolpiruvat + ADP +H+ Piruvat + ATP - + ATP Alanin Fruktosa 1,6-bisfosfat

  5. Pengendalian aktivitas enzimPiruvat-kinaseoleh F2,6 BP • Alaninsecaraallosterikmenghambatpiruvatkinase • Bilakadarglukosadarahmenurun, glukagonmemicukaskade AMP siklik yang menyebabkanfosforilasiPiruvatKinase, yang mengurangiaktivitasnya • Fosforilasiinisepertienzimbifungsi yang mengontrolkadarfruktosa 2,6-bisfosfat

  6. Fruktosa 2,6-bisfosfat dibentukmelaluifosforilasisenyawafruktosa 6-fosfat olehenzimfosfofruktokinase-2 • dalamkeadaanglukosa yang berlimpah, konsentrasisenyawafruktosa 2,6-bisfosfat akanmeningkatsehinggamerangsangglikolisisdenganmengaktifkan fosfofruktokinase-1 danmenghambat fruktosa-1,6-bisfosfatase. • Dalamkeadaankekuranganglukosa, glukoneogenesisdirangsangolehpenurunankonsentrasifruktosa 2,6-bisfosfat yang kemudianmenghilangkanaktivitas fosfofruktokinase-1 danmeniadakanpenghambatankerja fruktosa-1, 6-bisfosfatase.

  7. Pengendalian aktivitas enzimPiruvat-kinaseolehasamsitrat • PyruvateCarboxylase (pyruvateoxaloactate) is allostericallyactivated by acetyl CoA. • [Oxaloacetate] tends to be limiting for Krebs cycle.

  8. Enzymes relevant to these pathways that are phosphorylated by Protein Kinase A include: • PyruvateKinase, a glycolysis enzyme that is inhibited when phosphorylated. • CREB (cAMP response element binding protein) which activates, through other factors, transcription of the gene for PEP Carboxykinase, leading to increased gluconeogenesis. • A bi-functional enzyme that makes and degrades an allosteric regulator, fructose-2,6-bisphosphate.

  9. PFK activity in the presence of the globally controlledallosteric regulator fructose-2,6-bisphosphate is similar to that at low ATP. • Fructose-2,6-bisphosphate promotes the relaxed state, activating Phosphofructokinase even at high [ATP]. • Thus activation by fructose-2,6-bisphosphate, whose concentration fluctuates in response to external hormonal signals, supersedes local control by [ATP].

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