Eukaryotic and Prokaryotic Enzymes

Hexokinase or Glucokinase

catalyzes the phosphorylation of glucose to glucose-6-phosphate inhibited by its product occurs in the cytosol

Phosphofructokinase 1 (PFK1)

in cytoplasm converts fructose-6-phosphate to fructose-1,6-bisphosphate and is rate limiting step inhibited by ATP citrate and loq pH

Pyruvate Kinase

in cytosol catalyze final step of glycolysis converting phosphoenolpyruvate (PEP) to pyruvate and produces ATP inhibited by alanine, phenylalanine, and tryptophan

lactate dehydrogenase

found in cytoplasm converts pyruvate to lactate under anerobic condition to regenerate NAD⁺ for glycolysis.

Pyruvate Dehydrogenase Complex (PDC)

In mitochondrial matrix converts pyruvate into acetyl CoA links glycolysis to TCA cycle producing NADH and CO₂

Citrate Synthase

In MM catalyzes the condensation of oxaloacetate and acetyl CoA into citrate

Aconitase

In MM converts citrate to isocitrate by isomerization

Isocitrate dehydrogenase

In MM catalyzes the decarboxylation of isocitrate to a-ketoglutarate producing NADH and CO₂

a-ketoglutarate dehydrogenase

In MM in TCA cycle converts a-ketoglutarate to succinyl-CoA and produces NADH and CO₂

Succinyl-CoA synthetase

In MM catalyzes the conversion of Succinyl-CoA to Succinate and also generates GTP

Succinate Dehydrogenase

Mitochondrial membrane bond enzyme that converts succinate to fumarate making FADH₂ but also the name of CII

Fumarase

In MM catalyzes the hydration of fumarate into malate requires water input

Malate dehydrogenase

Converts malate to oxaloacetate and produces NADH

Complex 5

ATP Synthase found on the IMM synthesizes ATP from ADP using the proton gradient generated

Complex 1

NADH dehydrogenase transfers electrons from NADH to coenzyme Q (ubiquinone) and pumps protons into intermembrane space

Complex 2

Succinate Dehydrogenase IMM enzyme that oxidizes succinate to fumarate by producing FADH₂ and transfer enzymes to ubiquinone without proton pumping

Complex 3

Cytochrome bc1 complex, Transfers electrons from ubiquinol to cytochrome C and pumps protons

Complex 4

Cytochrome C oxidase, Reduces O₂ to water by ending the ETC and pumps protons into the Intermembrane space

glucose-6-phosphatase

removes phosphate from glucose-6-phospahte to produce glucose. Occurs during gluconeogenesis and glycogenolysis

Fructose-1,6-Bisphosphatase

In the cytoplasm removes a phosphate from fructose-1,6-Bisphosphate in gluconeogenesis and is inhibited by AMP

PEP carboxykinase (PEPCK)

converts oxaloacetate into phosphoenolpyruvate in gluconeogenesisp

pyruvate carboxylase

In mitochondria and converts pyruvate to oxaloacetate and is activated by acetyl-CoA

Glycogen Phosphorylase

In liver and muscle and breaks down glycogen into glucose-1-phosphate during glycogenolysis

Glycogen Synthase

In cytosol catalyzes the formation of a-1,4-glycosidic bonds in glycogen synthesis

Branch Enzyme

Adds a-1,6-glycosidic bonds or branches during glycogen synthesis

Debranching Enzyme

Removes a-1,6-glycosidic bonds during glycogenolysis

Amylase

found in saliva and pancreas and breaks down starches into maltose

Maltase

SI brush border enzyme that hydrolyzes maltose into two glucose molecules

Lactase

In SI breaks latose into glucose and galactose

Sucrase

Intestinal Brush border enzyme that breaks sucrose into glucose and fructose

Enterokinase

Also called enteropeptidase secreted by SI duodenal cells and activates trypsinogen to trypsin.

Trypsin

pancreatic enzyme activated in the small intestine that breaks down proteins and activates other zymogens

Chymotrypsin

pancreatic enzyme activated in the SI that digests peptide bonds next to aromatic residue

Carboxypeptidase

pancreatic enzyme that removes terminal AA’s by the carboxy end of proteinsp

pepsin

active in the stomach inactive version pepsinogen secreted in stomach by chief cells. Breaks down proteins into peptides. Activated by HCL from parietal cells. Hormone gastrin from G cells is secreted in presence of food and causes the secretion of HCl

lipase

secreted by the pancreas into the small intestine to digest triglycerides into FA’s and monoglycerides.

DNA polymerase III

Only Prokaryotes synthesizes new DNA strands during replication 5 to 3 direction and does some proofreading

DNA Polymerase I

Only Prokaryote it removes RNA primer and replaces that section with DNA

RNA Polymerase II

Only in Eukaryotes transcribes mRNA from DNA templates in the nucleus

DNA ligase

joins Okazaki fragments during DNA replication by forming phosphodiester bonds

Topoisomerase

relieves supercoiling ahead of replication forks by cutting a small portion of DNA

Helicase

unwinds and unzips DNA at replication origin

Primerase

Synthesizes RNA primers required for DNA polymerase to initiate replication

Reverse transcriptase

in retro viruses and rt-PCR which synthesizes DNA from mRNA

Telomerase

ribonucleoprotein that adds repetitive DNA sequences to the ends of eukaryotic chromosomes to prevent shortening

adenylate cyclase

membrane bound enzyme that converts ATP to cAMP in response to GPCR signaling

protein Kinase A (PKA)

Activated by cAMP it phosphorylates various proteins in metabolic regulation

protein phosphatase

removes phosphate from proteins performing the reverse action of kinases

Ureases

produced in some bacteria (H. pylori) which hydrolyzes urea into NH₄⁺ and CO₂ raising local pH

Coenzyme Q

Also called ubiquinone lipid soluble electron carrier that transports electrons from CI and CII to CIII

Cytochrome C

A water soluble electron carrier located in the intermembrane space of the mitochondria transfers electrons from CIII to CIV and also is involved with apoptosis

DNA polymerase a (alpha)

eukaryotic enzyme that initiates DNA replication by adding a short RNA to DNA primer to the lagging strand

DNA polymerase δ (Delta)

eukaryotic enzyme that extends lagging strand after primer synthesis and has some proofreading ability

DNA polymerase ε (epilison)

eukaryotic enzyme responsible for leading strand synthesis and also participates in DNA repair

Transferase

Broad class of enzyme that transfers functional groups (methyl or phosphate) from one molecule to another. kinases are a specific type of transferase

lyases

Enzymes that break chemical bonds like C-C, C-O, C-N WITHOUT using H₂O or oxidation usually by forming a double bond or ring structure

Hydrolase

Catalyzes cleavage of bonds using water (hydrolysis), including proteases, lipases, and nucleases

Oxidoreductases

Enzymes that catalyze redox reactions transferring of electrons which typically include dehydrogenases or oxidases

Isomerases

Rearranges atoms within a molecule to create an isomer

Phosphodiesterase (PDE)

Break phosphodiester bonds in cyclic nucleotides like cAMP and cGMP thereby terminating second messenger systems

Phospholipases

Cleaves phospholipids releasing diacylglycerol (DAG) adn inorganic phosphate important in secondary messenger systems.

Difference between Kinase, phosphorylase, and Phosphatase

Kinase: Adds a phosphate from ATP to a substrate

Phosphorylase: Adds a phosphate group from inorganic phosphate

Phosphatase: Removes a phosphate group from a molecule by hydrolysis reverse kinase

nuclease

an enzyme that cleaves the phosphodiester bonds within nucleic acids, such as DNA and RNA

Tyrosine kinase

Associated with a membrane receptor for insulin and growth factor responses. This receptor auto phosphorylates upon ligand binding and activates intracellular signaling

Aromatase

Located in the ovary, placenta, adipose tissue, and brain which converts androgens to estrogens

adenylyl cyclase

membrane bound enzyme activated by GPCR converting ATP to cAMP

Guanylyl cyclase

found in smooth muscle and kidneys converts GTP to cGMP in response to NO nitric oxide or natriuretic peptides, regulating vasodilation and fluid balance

Thrombin

Synthesized from prothrombin in the liver activated in blood and converts fibrinogen to fibrin for the clotting process

Plasmin

In blood and dissolves fibrin clots

Capases

located in cytoplasm and activated during apoptosis by intrinsic mitochondrial signaling or extrinsic death receptor pathways

Cytochrome P450

family of liver ER membrane enzymes that oxidize drugs, toxins and steroids

Alcohol dehydrogenase

coverts alcohol in the liver into acetaldehyde which is an ROS

Aldehyde dehydrogenase (ALDH)

oxidize acetaldehyde to acetate

Acetyl CoA carboxylase (ACC)

enzyme in liver and adipose tissue that converts acetyl coA to malonyl coA in fatty acid synthesis upregulated by insulin down regulated by glucagon.

B-lactamase

Secreted by some bacteria breaks down certain antibiotics like penicillin and can lead to antibiotic resistance.

transpeptidase

bacterial enzyme in the periplasmic space of the cell wall that forms peptidoglycan cross links for wall stability. Usually targeted by antibiotics.