Peptide vs Protein: Understanding the Molecular Differences

# Introduction Peptides and proteins are both fundamental components of cells that play crucial roles in various biological functions. Although they are both made up of amino acids linked by peptide bonds, they differ in terms of their size, structure, and function [3]. Understanding the molecular differences between peptides and proteins is crucial for various fields, including drug development, biochemistry, and disease diagnosis and treatment [10]. # Peptides Peptides are short chains of amino acids, typically comprising 2-50 amino acids [10]. They are synthesized in the body and can be found in every cell and tissue. Peptides play several roles, including acting as biochemical messengers, modulating immune responses, and regulating physiological functions [10]. For example, angiotensin-(1-7), a peptide hormone, has been found to be upregulated in human podocytes, cells critical for kidney function, under fluid flow shear stress [1]. Peptides can also be synthesized in the lab for research and therapeutic purposes. For instance, pepADMET, a computational platform, has been developed for systematic Absorption, Distribution, Metabolism, Excretion, and Toxicity (ADMET) evaluation of peptides [10]. # Proteins Proteins are large, complex molecules composed of one or more long chains of amino acids, typically more than 50 [3]. They are responsible for nearly every function of living organisms, from structural support to immune defense and cellular communication. Proteins can act as enzymes, hormones, antibodies, and receptors, among other roles [2][3]. For example, Triggering Receptor Expressed on Myeloid Cells 1 (TREM1) is a protein involved in inflammatory responses. Inhibition of TREM1 was found to attenuate myocardial ischemia-reperfusion injury-induced cardiomyocyte pyroptosis, a form of programmed cell death, by suppressing the activation of the NF-κB signaling pathway [2]. # Preclinical Research Preclinical research provides insight into the cellular and molecular mechanisms underlying the biological roles of peptides and proteins. For instance, studies on angiotensin-(1-7) peptides have revealed their importance in kidney function [1]. Similarly, investigations into the TREM1 protein have elucidated its role in inflammation and cell death [2]. Chemogenetic approaches have also been employed to activate endogenous G-protein-coupled receptors (GPCRs), a large family of proteins, allowing for temporal and cell-specific studies of their function in vivo [8]. However, there is currently no direct preclinical evidence in the provided citations comparing the effects of peptides and proteins. # Clinical Evidence Clinical evidence supports the importance of both peptides and proteins in disease diagnosis and treatment. For instance, misfolded proteins have been identified as biomarkers in neurodegenerative diseases [9]. However, the provided citations do not offer direct clinical evidence comparing the effects of peptides and proteins in humans. # Safety and Limitations While peptides and proteins play crucial roles in biological functions and therapeutic applications, there are safety considerations and limitations to their use. The ADMET profile of peptides, which predicts how they will be absorbed, distributed, metabolized, excreted, and potentially toxic, is one important consideration [10]. For proteins, factors such as their large size, complex structure, and potential for eliciting immune responses can present challenges for their use as therapeutics [2][3]. However, the provided citations do not provide a comprehensive comparison of the safety and limitations of peptides versus proteins. # Key Takeaways Peptides and proteins, though composed of amino acids, differ significantly in their size, structure, and function. Peptides, as short chains of amino acids, play roles as messengers and regulators of physiological functions. Proteins, with their larger size and complexity, carry out a wider range of functions, including enzymatic activity, hormonal regulation, and immune defense. Preclinical research has underscored the importance of both peptides and proteins in understanding cellular and molecular mechanisms. However, direct preclinical and clinical evidence comparing the effects of peptides and proteins is not available in the provided citations. Safety considerations and limitations exist for both peptides and proteins, with peptides requiring comprehensive ADMET profiling and proteins presenting challenges due to their size and complexity. As our knowledge of these biomolecules continues to grow, so too will their therapeutic potential.