Gluten is a type of protein found in wheat and related grains such as rye and barley, making up about 80% of their total protein content. Normally, proteins are digested in the stomach and upper small intestine (duodenum). However, gluten’s structure renders it highly resistant to most of our digestive enzymes, allowing fragments of the gluten protein to persist in the small intestine. More specifically, the gluten protein contains long stretches of proline and glutamine amino acids that require special enzymes to break apart, which humans do not possess. Interestingly, research has identified numerous microbes in both the mouth and colon that can degrade gluten.
It is estimated that at least 1% of the U.S. population suffers from celiac disease, an autoimmune condition characterized by the destruction of the small intestine in response to gluten. Immediate symptoms may include gastrointestinal (GI) distress, headaches, and muscle aches. And long-term gluten consumption can lead to malnutrition, weight loss, and possibly death. The only known treatment option is a lifelong gluten-free diet. However, many foods may contain hidden or unexpected sources of gluten, and food labels on products are not always present. Even items labelled “gluten-free” only need to be below a certain threshold, making them not truly gluten-free. And although non-celiac gluten sensitivity is a controversial diagnosis, research suggests that gluten may damage the guts of people who don’t have celiac disease (as explored in Study Deep Dives issues #7 and #8).
There has been a recent interest in prolyl endopeptidases (PEP, shown in Figure 1), which are a type of enzyme capable of breaking down the proline-glutamine chains within gluten. While early research suggests that PEPs derived from bacteria don’t function well due to the stomach’s acidity, are rapidly broken down by our own digestive enzymes, and are unable to efficiently prevent the passage of gluten through the intestinal tract, there has been increasing interest of PEPs derived from alternative sources.
In this respect, the Aspergillus niger-derived PEP (AN-PEP) has shown promising cell culture results. Additionally, it has proved itself in a digestive model that closely mimics the human GI tract. Most recently, AN-PEP appeared to be well-tolerated in celiac disease patients consuming gluten daily for two weeks, but its efficiency compared to placebo could not be evaluated. The authors of the study under review sought to evaluate how efficiently AN-PEP breaks down gluten in the stomachs of healthy volunteers.
Gluten is a digestion-resistant protein found in wheat and related cereal grains that can cause extreme distress for people with celiac disease. This study evaluated how efficiently a type of enzyme called AN-PEP breaks down gluten in the stomachs of healthy volunteers.