-enzyme remove a phosphate from a protein

-turn off a protein

-inactive signaling molecule**

-Dephosphorylation occur

PKA phosphorylates transcription factors, including CREB and NFκB

deactivation of PKA as the regulatory subunits rebind to the catalytic subunits, returning them to an inactive state

Second messenger: cGMP

Deactivation of PKG as the regulatory subunits rebind to catalytic subunits, returning them to an inactive state.

In the presence of Ca²⁺-calmodulin binding, CaMKII activation involves autophosphorylation.

Protein phosphatases
-dephosphorylate the target proteins, reversing the effects of CaMK-mediated phosphorylation and deactivated.

Activation of some PKC forms can also be through PI-3kinase pathway

Function: insulin signaling. Inhibition of AMPK in the presence of glucose can activate insulin secretion.

acts as sensor for cellular energy status in some cells

If haem is present, kinase not active as haem binds to it, protein synthesis occurs

Turn on :Phophotidylinositol 3-kinase (inositol pathway), GTPase-activating protein (G-Protein signaling) and mitogen activated protein kinase cascades (MAP kinases)

Involve in：
-Vascular Endothelial Growth Factor (VEGF)
-Neurotrophins
-Insulin-like Growth Factor-1 (IGF-1)

contain tyrosine phosphorylation capacity which membrane bound, soluble and reside in the cytoplasm of the cell or associated with the membrane proteins

The STAT dimers move to nucleus to bind to DNA and regulate gene transcription.

In humans there are at least seven different STAT proteins and seven JAK homology domains

Soluble, associated with the cytoplasm

extracellular domain , a transmembrane domain and domain containing phosphatase activity

These enzymes catalyze the removal of a phosphate group from a tyrosine residue using a cysteinyl-phosphate enzyme intermediate

Important in controlling cell growth, proliferation, differentiation, transformation, and synaptic plasticity.

PP2B
*PP2B(calcineurin) heterodimer (calcium dependent enzyme

PPA2
trimeric protein and have similarities to PP1 Include the control of DNA replication and apoptosis

Cell proliferation,cell death, embryonic development and cell differentiation

PP1
Has broad substrate specificity Catalytic subunits of 37 kDa inhibit activity og PP1
Involved in regulation of glycogen (under control of phosphorylation)metabolism PP1 is under control of cAMP signaling pathway

Triacylglycerol Lipase (TG Lipase): This enzyme catalyzes the hydrolysis of triacylglycerol (TAG) into free fatty acids and glycerol, which can be used for energy production. TG lipase is highly active in adipose tissue, where it mobilizes stored fats during fasting or exercise.

Hormone-Sensitive Lipase (HSL): HSL is an enzyme that is activated in response to hormonal signals like adrenaline and glucagon. It breaks down stored triglycerides in adipocytes (fat cells) to release fatty acids for energy production during periods of low carbohydrate availability.

Pancreatic Lipase: This enzyme is critical for the digestion of dietary fats. It breaks down triglycerides in the small intestine into monoglycerides and free fatty acids, which can be absorbed by the intestinal cells.

Phospholipase A2 (PLA2): PLA2 enzymes hydrolyze the sn-2 acyl bond of phospholipids, releasing arachidonic acid, a precursor for eicosanoids (prostaglandins, thromboxanes, leukotrienes). These signaling molecules are involved in inflammation and other physiological processes.

Phospholipase C (PLC): PLC enzymes cleave the phosphodiester bond of phosphatidylinositol 4,5-bisphosphate (PIP2), generating inositol triphosphate (IP3) and diacylglycerol (DAG). IP3 mediates calcium release from intracellular stores, while DAG activates protein kinase C (PKC), both of which are important for signal transduction.

Phospholipase D (PLD): PLD hydrolyzes phosphatidylcholine (PC) to produce phosphatidic acid (PA) and choline. PA is a lipid second messenger that plays a role in membrane trafficking, cytoskeletal organization, and cell signaling.

FAS: Fatty Acid Synthase is a multi-enzyme complex that catalyzes the synthesis of long-chain fatty acids from acetyl-CoA and malonyl-CoA in the cytosol. It is crucial in adipocytes for the storage of energy as fat and in the liver for the synthesis of fatty acids that are incorporated into lipoproteins.

Acid Sphingomyelinase (ASM): This enzyme hydrolyzes sphingomyelin, a type of sphingolipid found in cell membranes, to produce ceramide. Ceramide is a bioactive lipid that plays a role in apoptosis (programmed cell death), cell growth arrest, and inflammation.

Neutral Sphingomyelinase (NSM): NSM also hydrolyzes sphingomyelin to generate ceramide but operates optimally at a neutral pH. It is involved in signal transduction pathways that regulate cell stress responses.

LPL: Lipoprotein lipase is an enzyme located on the endothelial surface of capillaries in adipose tissue, muscle, and the heart. It hydrolyzes triglycerides in circulating chylomicrons and very low-density lipoproteins (VLDL) into free fatty acids, which are then taken up by cells for energy or storage.

Cholesteryl Ester Hydrolase (CEH): CEH enzymes catalyze the hydrolysis of cholesteryl esters to free cholesterol and fatty acids. This reaction is essential in the mobilization of cholesterol from intracellular stores, particularly in steroidogenic tissues where cholesterol is a precursor for steroid hormones.

Hormone-Sensitive Cholesteryl Esterase: Similar to hormone-sensitive lipase, this enzyme is activated by hormonal signals and plays a crucial role in the regulation of cholesterol homeostasis, particularly during stress or fasting.

Stearoyl-CoA Desaturase (SCD): SCD introduces a double bond into saturated fatty acyl-CoAs, producing monounsaturated fatty acids (MUFAs) like oleic acid. These MUFAs are key components of membrane phospholipids, triglycerides, and cholesterol esters.

Delta-5 and Delta-6 Desaturases: These enzymes are involved in the biosynthesis of polyunsaturated fatty acids (PUFAs) from essential fatty acids like linoleic acid and alpha-linolenic acid. PUFAs are important for the fluidity of cell membranes and serve as precursors for eicosanoids, which have various signaling roles in inflammation and immunity.

Phosphatidylinositol-4-Phosphate 5-Kinase (PIP5K): This enzyme phosphorylates phosphatidylinositol 4-phosphate (PI4P) to produce phosphatidylinositol 4,5-bisphosphate (PIP2), a crucial lipid that serves as a substrate for PLC and regulates various cellular processes, including cytoskeletal organization and membrane trafficking.

Diacylglycerol Kinase (DGK): DGK phosphorylates diacylglycerol (DAG) to produce phosphatidic acid (PA). This reaction is critical in terminating DAG-mediated signaling and in generating PA, which has signaling functions in its own right.

Acid Lipase: Found in lysosomes, this enzyme is responsible for breaking down cholesteryl esters and triglycerides within lysosomes, releasing free cholesterol and fatty acids that can be used by the cell. Mutations in this enzyme can lead to lysosomal storage diseases like Wolman disease and cholesteryl ester storage disease.

Ceramide Synthases: These enzymes catalyze the formation of ceramide from sphinganine (a long-chain base) and fatty acyl-CoA. Ceramide is a central molecule in sphingolipid metabolism and plays important roles in regulating cell growth, differentiation, and apoptosis.

ACC1 and ACC2: ACC is a key enzyme in the biosynthesis of fatty acids. It catalyzes the carboxylation of acetyl-CoA to form malonyl-CoA, the first committed step in fatty acid synthesis. ACC1 is primarily involved in lipogenesis (fatty acid synthesis), while ACC2 regulates fatty acid oxidation by controlling the levels of malonyl-CoA, which inhibits carnitine palmitoyltransferase 1 (CPT1), the enzyme responsible for transporting fatty acids into mitochondria for oxidation.

Acyl-CoA Synthetase (ACS): This family of enzymes activates fatty acids by attaching them to Coenzyme A (CoA), forming acyl-CoA. This activation is necessary for the fatty acids to participate in various metabolic pathways, including β-oxidation, where they are broken down to generate ATP.

Long-Chain Acyl-CoA Synthetase (ACSL): ACSL enzymes specifically activate long-chain fatty acids. These activated fatty acids can then be used for the synthesis of complex lipids like triglycerides or for energy production through β-oxidation.

signal dilation of blood vessels

Activation of Transcription Factors: As the signal transduction pathway progresses, it frequently leads to the activation or inhibition of transcription factors. This activation can occur through various mechanisms, including phosphorylation (addition of phosphate groups), binding of signaling molecules, or changes in cellular localization.

Signal Transduction: The binding of the signal to its receptor triggers a cascade of intracellular events. This can involve various proteins, second messengers, and other molecules that relay and amplify the signal.

Gene Regulation: Once activated, transcription factors move into the nucleus (if they are not already there) and bind to specific DNA sequences in the promoter or enhancer regions of target genes. This binding can either promote or inhibit the transcription of these genes into mRNA.

Feedback and Regulation: Transcription factors can also play roles in feedback loops, where they regulate the expression of other components in the signaling pathway to ensure the proper level of response and prevent overreaction.