PAM

What is PAM protein?

PAM gene (peptidylglycine alpha-amidating monooxygenase) is a protein coding gene which situated on the long arm of chromosome 5 at locus 5q21. This gene encodes a multifunctional protein. The encoded preproprotein is proteolytically processed to generate the mature enzyme. This enzyme includes two domains with distinct catalytic activities, a peptidylglycine alpha-hydroxylating monooxygenase (PHM) domain and a peptidyl-alpha-hydroxyglycine alpha-amidating lyase (PAL) domain. These catalytic domains work sequentially to catalyze the conversion of neuroendocrine peptides to active alpha-amidated products. The PAM protein is consisted of 973 amino acids and PAM molecular weight is approximately 108.3 kDa.

What is the function of PAM protein?

PAM is a component of the bacterial outer membrane, where it forms channels that allow the passive diffusion of molecules across the membrane. As a porin, PAM helps in the selective permeation of nutrients and other molecules into the bacterial cell, depending on their size and charge. The PAM protein may also play a role in helping the bacterium evade the host immune system by facilitating the transport of immunosuppressive molecules or avoiding the detection by immune cells. Pseudomonas aeruginosa is known for its resistance to serum complement-mediated killing. PAM, as part of the outer membrane, may contribute to this serum resistance. PAM may also be involved in the formation and maintenance of biofilms, which are complex bacterial communities embedded in a self-produced matrix that provide additional protection to the bacteria from the environment and antibiotics.

Fig1. PAM interactors. (Nils Bäck, 2022)

PAM Related Signaling Pathway

PAM may be involved in signaling pathways that facilitate bacterial adherence to host cells, which is a critical step in the invasion process. P. aeruginosa uses various strategies to evade the host immune response, and PAM's role in the outer membrane may contribute to these immune evasion tactics by affecting how the immune system recognizes and responds to the bacterium. PAM could be implicated in signaling pathways that regulate biofilm formation, a protective environment for bacteria that is resistant to antibiotics and the host immune system. The outer membrane porins, including PAM, may be involved in the bacterium's response to environmental stress, such as changes in nutrient availability or the presence of antimicrobial agents. PAM's role in the permeability of the outer membrane could affect signaling pathways related to antimicrobial resistance by influencing the uptake of antibiotics.

PAM Related Diseases

In endocrine disorders such as primary hyperparathyroidism, PAM is involved in post-modification of parathyroid hormones, affecting their ability to regulate calcium and phosphorus metabolism. The processing effect of PAM on vasoactive peptides may affect blood pressure regulation, which is related to cardiovascular diseases such as hypertension. Due to the role of PAM in neuropeptide processing, abnormalities in PAM may be associated with neurodegenerative diseases such as Alzheimer's disease. At the same time, PAM is also associated with pain perception, digestive system diseases, kidney diseases and so on.

Bioapplications of PAM

PAM plays a key role in the synthesis of various bioactive peptides, and these peptide hormones have potential applications in the treatment of cardiovascular diseases such as hypertension and heart disease, so PAM can be used as a target for the development of novel drugs. PAM is used to produce amylated peptide hormones that play an important role in regulating physiological functions, such as regulating blood pressure and affecting pain perception. Changes in the activity or expression level of PAM may be associated with certain disease states and can therefore be used as biomarkers for disease diagnosis and monitoring. PAM is used in the field of biotechnology to modify and optimize peptide drugs to improve their stability and bioavailability.

Case Study 1: Vishwanatha K S Rao, 2021

Using the production of amidated chromogranin A to monitor PAM function in tumor cells, physiologically relevant levels of hypoxia were shown to inhibit this monooxygenase. The ability of primary pituitary cells exposed to hypoxic conditions for 4 h to produce amidated chromogranin A was similarly inhibited. The affinity of the purified monooxygenase for oxygen was consistent with this result. The ability of PAM to alter secretory pathway behavior under normoxic conditions required its monooxygenase activity. Under normoxic conditions, hypoxia-inducible factor 1a levels in dense cultures of corticotrope tumor cells expressing high levels of PAM exceeded those in control cells; expression of inactive monooxygenase did not have this effect. Putative hypoxia response elements occur in both human and mouse PAM, and hPAM has consistently been identified as one of the genes upregulated in response to hypoxia. Expression of PAM is also known to alter gene expression. A quarter of the genes consistently upregulated in response to hypoxia were downregulated following increased expression of PAM.

Fig1. Cell density affects Hif1a expression differently in WT and AtT-20/PAM1 cells.

Fig2. Atf3 are affected oppositely by hypoxia and by high PAM expression.

Case Study 2: Peter D Simpson, 2015

Interactions between biological pathways and molecular oxygen require robust mechanisms for detecting and responding to changes in cellular oxygen availability, to support oxygen homeostasis. Peptidylglycine α-amidating monooxygenase (PAM) catalyzes a two-step reaction resulting in the C-terminal amidation of peptides, a process important for their stability and biological activity. Here researchers show that in human, mouse, and insect cells, peptide amidation is exquisitely sensitive to hypoxia. Different amidation events on chromogranin A, and on peptides processed from proopiomelanocortin, manifest similar striking sensitivity to hypoxia in a range of neuroendocrine cells, being progressively inhibited from mild (7% O2) to severe (1% O2) hypoxia. In developing Drosophila melanogaster larvae, FMRF amidation in thoracic ventral (Tv) neurons is strikingly suppressed by hypoxia.

Fig3. Supplementation of culture medium with ascorbate or copper does not alter the sensitivity of PAM to oxygen concentration.

Fig4. Validation of PAM mRNA and protein knockdown following PAM siRNA treatment of AtT20 cells.

PAM has several biochemical functions, for example, L-ascorbic acid binding,copper ion binding,peptidylamidoglycolate lyase activity. Some of the functions are cooperated with other proteins, some of the functions could acted by PAM itself. We selected most functions PAM had, and list some proteins which have the same functions with PAM. You can find most of the proteins on our site.

PAM has direct interactions with proteins and molecules. Those interactions were detected by several methods such as yeast two hybrid, co-IP, pull-down and so on. We selected proteins and molecules interacted with PAM here. Most of them are supplied by our site. Hope this information will be useful for your research of PAM.

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