BioChem Chapter 14 pt. 2: Pentose Phosphate Pathway & Regulation

What are the two pathways of the pentose phosphate pathway simplified?

non-oxidative and oxidative phase

all enzymes of the pentose phosphate pathway are located in the ____ space

cytosolic

what is the starting substrate of the phosphate pathway?

glucose-6-phosphate

what is one cofactor difference in the phosphate pathway?

uses NADP+ and NADPH

what is glutathione reductase?

reducing agenst that helps with oxidative stress in the phosphate pathway

in phosphate pathway, NADPH still accepts ___ but the phosphate makes the enzyme more ____.

hydride

specific

Pentose phosphate pathway:

-NADPH is an electron ____

-reductive biosynthesis of ___ ___ and ____

-repair of ____ damage

donor

fatty acids and steroids

oxidative

Pentose phosphate pathway:

-ribose-5-phosphate is a biosynthetic precursor of ____

-used in ___ and ____ synthesis

-or synthesis of some ____

nucleotides

DNA and RNA

coenzymes

Pentose phosphate pathway:

-___ phase generates NADPH and a pentose

oxidative

NADPH regulates partitioning into ____ glycolysis versus pentose phosphate pathway

glycolysis

_____NADPH concentration slows sown pentose phosphate pathway

high

high _____ stimulates pathway via glucose-6-phosphate dehydrogenase

NADP+

NADPH needed to protect against ____ stress

oxidative

Pentose phosphate pathway:

-superoxide radical, hydrogen peroxide, and hydrogen free radical are all ____ and cause ___, disturbing pathways

reactive

damage

Pentose phosphate pathway:

-to prevent oxidative stress, what does glutathione peroxidase do?

reduces hydrogen peroxide to water

Pentose phosphate pathway:

-to prevent oxidative stress, NADPH is used as a substrate for ____ ____

glutathione reductase

What is the oxidized form of glutathione?

sulfide form

What is the reduced form of glutathione?

a thiol

_____ enzymes often correspond to points in the pathway that have the same substrate and product, but a different ____

regulated

enzyme

Regulatory enzymes:

-glycolysis: going from glucose to glucose-6-phosphate uses ____

-gluconeogenesis: going from glucose-6-phosphate to glucose uses _____

hexokinase

glucose-6-phosphatase

Regulatory enzymes:

-glycolysis: going from gructose-6-phosphate to fructose-1,6-biphosphate uses____

gluconeogensis: going fron fructose-1,6-biphosphate to fructose-6-phosphate uses____

phosphofructokinase-1 (PFK-1)

fructose-1,6-biphosphatase-1

Regulatory enzymes:

-glycolysis: going from phosphenolpyruvate (PEP) to pyruvate uses ____

-gluconeogenesis: going from pyruvate to oxaloacetate uses ____ the to phosphoenolpyruvate (PEP) uses _____

pyruvate kinase

pyruvate carboxylase; PEP carboxykinase

there are four ____ of HExokinase (I-IV)

isozymes

HK I is expressed in all ____, to different levels

tissues

HK IV (ex: glucokinase) is only expressed in the ____

liver

HK IV:

-has higher ___ (bonding affinity), so responsive to higher [glucose]

-not ___ by glucose-6-phosphate, so can function as higher [glucose]

-functions to clear ____ glucose at higher [glucose] for storage as ____

Km

inhibited

blood; glycogen

____ are different enzymes that catalyze the ____ reaction:

-typically share similar____

-may have different. _____ properties

-can be ____ differently

isozymes

same sequences

kinetic

regulated

higher Km → _____binding

weaker

HK IV: higher Km doesn’t ____ as easily, can consume more ____

saturate

glucose

hexokinase IV is regulated by ___ (and ___ ) - what does this mean?

sequestration

transcription

-depends what is bound to within the cell such as regulatory protein

HK IV: different ____ properties is a way of regulation

kinetic

What is the commitement step in glycolysis?

Fructose-6-phosphate to fructose-1,6-biphosphate

Regulation of PFK-1:

-while ATP is a ___, ATP is also a ____ effector

-do not spend glucose in glycolysis if there is plenty of ____

substrate

negative

APT

lots of ____ regulation for PRK-1

allosteric- conformational change which changes the activity

regulation of PFK-1:

-what are examples of negative effectors?

-what are examples of positive effectors?

neg: ATP and citrate

pos: AMP, ADP, and fructose-2,6-biphosphate

PFK-1 give a ____ curve with allosteric enzyme

sigmoidal

PFK-1 with high ATP ____. flux;

PFK-1 with low ATP ____

Decrease

normal

Regulation of phosphofructokinase-1 and fructose-1,6-biphosephatase:

-go glycolysis if AMP is ___ and ATP is ____

-go gluconeogenesis if AMP is ____

-PFK-1 is more _____

high; low

low

regulated

fructose-2,6-biphosphate:

-____ a glycolytic intermediate, only a ____

NOT

regulator

fructose-2,6-biphosphate:

-produced specifically to regulate ___ and ___

-____ phophofructokinase (glycolysis)

-_____ fructose-1,6- biphosphatase (gluconeogenesis)

glycolysis and gluconeogenesis

activates

inhibits

When there is fructose-2,6-biphosphate with PFK-1 is the curve higher or lower with or without? what pathway?

higher with F-2,6-bP

glucose

When there is fructose-2,6-biphosphatate with fructose-1,6-biphosphatase is the curve higher or lower with or withour?

higher without F-2,6-bP

gluconeogenesis

What is fructose-2,6-biphosphate produced from?

fructose-6-phosphate with help of PFK-2 (promote glycolysis)

what is needed to breakdown fructose-2,6-biphosphate to fructose-6-phonsphate

FBPase-2 (promote glycolysis)

regulation of f-2,6-bP levels:

structurally PFK-2 and FBPase-2 are different than those in glycolysis and gluconeogenesis, (they are ___) and are regulated via _____

conjoined

phosphorylation

When PFK-2 is active what forms?

fructose-2,6-biphosphate

When FBPase-2 is active what forms

fructose-6-phosphate

active PFK-2, increases F-2,6-bP ____ glycokysis and ____ gluconeogenesis

stimulates

inhibits

active FBPase-2, decreases F-2,6-bP ____ glycolysis and _____ gluconeokenesis

inhibits

stimulates

What is posistive activator for FBPase-2 (less F-2,6-bP)

glucagon-phosphorylation

what is positive activator for PFK-2 (more F-2,6-bP)

insulin-dephosphorylation

regulation of pyruvate kinase:

-____ activated by fructose-1,6-biphosphate

-____ flow through glycolysis

allosterically

increase

regulation of pyruvate kinase:

-allosterically inhibited by signs of abundant ___ aupply (all tissues)

-____

-___ ____ and long chain fatty acids

-____ (enough amino acids)

energy

ATP

Acetyl CoA

alanine

regulation of pyruvate kinase:

-inactived by ____ in response to signs of _____ depletion (glucagon) (liver only)

-glucose from liver is exported to the ___ and other vital organs

phosphorylation

glucose

brain

Regulation of pyruvate kinase: only ____ pyruvate kinase is inactivated by phosphorylation

liver