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Protein Digestion

Protein Digestion

Protein digestion begins in the stomach, where the highly acidic environment can easily disrupt protein structure by exposing the peptide bonds of polypeptide chains. After polypeptide chains are broken into individual amino acids by a series of digestive enzymes, the amino acids are transported to the liver via the bloodstream to produce energy.

Protein Kinases and Phosphatases

Protein Kinases and Phosphatases

Proteins undergo chemical modifications that trigger changes in the charge, structure, and conformation of the proteins. Phosphorylation, acetylation, glycosylation, nitrosylation, ubiquitination, lipidation, methylation, and proteolysis are various protein modifications that regulate protein activity. Such modifications are usually enzyme-driven.
Protein kinases
Many proteins in the cell are regulated by phosphorylation, the addition of a phosphate group. A family of enzymes called kinases...

Proteins: Dietary Sources and Requirements

Proteins: Dietary Sources and Requirements

Consuming animal-based products offers high-quality proteins that contain optimal levels and combinations of essential amino acids, crucial for tissue repair and growth. Foods like eggs, milk, fish, and most meats are a source of complete proteins. Legumes and cereals are abundant in proteins; however, they typically lack a full range of essential amino acids. As a result, they are considered incomplete protein sources. Some plant sources like soybeans, quinoa, and amaranth do contain complete...

Overview of Protein Metabolism

Overview of Protein Metabolism

Proteins are broken down into amino acids during digestion. Unlike fats and carbohydrates, which are stored for later use, proteins are not. Instead, amino acids are either used to produce ATP through oxidation or contribute to the creation of new proteins for the growth and repair of the body. Any surplus amino acids from the diet are converted into glucose or triglycerides rather than excreted.
Amino acids play various roles in the body once they are absorbed into cells. They are restructured...

Protein Absorption

Protein Absorption

Proteins in the gastrointestinal tract typically come from food, but they can also originate from disintegrated cells or secreted enzymes. In the stomach, the enzyme pepsin breaks down these proteins into polypeptides. The fragments then move into the duodenum as a semi-fluid mass called chyme. Pancreatic proteases, such as trypsin and chymotrypsin, and intestinal brush border enzymes like carboxypeptidases further dismantle the polypeptides into tripeptides, dipeptides, and free amino acids.

Amino Acid Catabolism

Amino Acid Catabolism

Microorganisms rely on proteins as an essential carbon and energy source, particularly in environments with limited polysaccharides or lipids. However, proteins are too large to cross the plasma membrane unaided, necessitating enzymatic degradation. Microbes secrete extracellular proteases and peptidases that hydrolyze proteins into peptides, which can then be transported across the membrane. Once inside the cell, intracellular proteases degrade these peptides into free amino acids, which...

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Related Experiment Video

Updated: Jul 13, 2026

A Facile Protocol to Generate Site-Specifically Acetylated Proteins in Escherichia Coli

A Facile Protocol to Generate Site-Specifically Acetylated Proteins in Escherichia Coli

Published on: December 9, 2017

Phytic acid and phytase: implications for protein utilization by poultry.

A J Cowieson¹, T Acamovic, M R Bedford

¹Avian Science Research Centre, Scottish Agricultural College, Ayr, UK.

Poultry Science

|May 6, 2006

Summary

Myo-inositol hexaphosphate (IP6) reduces broiler casein digestibility, but phytase supplementation can improve nutrient utilization. This study investigated IP6 and phytase effects on broiler chicken nutrient digestibility and mineral excretion.

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Area of Science:

Animal Nutrition
Nutrient Digestibility
Enzyme Technology

Background:

Myo-inositol hexaphosphate (IP6) is a common plant-derived anti-nutrient.
Phytase (EC 3.1.3.26) is an enzyme that degrades phytate.
Understanding their interaction is crucial for optimizing broiler feed formulations.

Purpose of the Study:

To investigate the effects of IP6 and phytase on casein digestibility in broiler chickens.
To assess the impact on nutrient (DM, N, amino acids, minerals) digestibility and phytate-P excretion.

Main Methods:

Precision feeding study with 64 Ross broiler chickens.
Groups were fed casein with varying levels of IP6 and phytase.
Excreta were collected over 48 hours to determine nutrient digestibility coefficients.

Main Results:

IP6 significantly reduced the digestibility of DM, N, and amino acids in casein.
Phytase supplementation improved amino acid digestibility compared to IP6 alone.
IP6 increased endogenous mineral excretion, which was reduced by phytase.

Conclusions:

IP6 ingestion negatively impacts casein digestibility and nitrogen utilization in broilers.
Phytase addition can partially mitigate the adverse effects of IP6 on protein utilization.
These findings support the use of phytase in broiler diets containing IP6.