Multifunctional peptides encrypted in milk proteins

Food-derived peptides with biological activity: from research to food applications

Many peptides that are released in vitro or in vivo from animal or plant proteins are bioactive and have regulatory functions in humans beyond normal and adequate nutrition. Different health effects have been attributed to food-derived peptides, including antimicrobial properties, blood pressure-lowering (ACE inhibitory) effects, cholesterol-lowering ability, antithrombotic and antioxidant activities, enhancement of mineral absorption and/or bioavailability, cyto- or immunomodulatory effects, and opioid activities. Numerous products are already on the market or under development by food companies that exploit the potential of food-derived bioactive peptides and which ascribe scientifically evidenced health claims to consumption of these functional foods.

The cryptome: a subset of the proteome, comprising cryptic peptides with distinct bioactivities

There is increasing evidence that proteolytic cleavage gives rise to 'hidden' peptides with bioactivities that are often unpredicted and totally distinct to the parent protein. So far, the liberation of these cryptic peptides, or crypteins, has been shown to be prevalent in proteins associated with endocrine signalling, the extracellular matrix, the complement cascade and milk. A broad spectrum of proteases has been implicated in the generation of natural crypteins that appear to play a role in modulating diverse biological processes, such as angiogenesis, immune function and cell growth. The proteolytic liberation of crypteins with novel activities represents an important mechanism for increasing diversity of protein function and potentially offers new opportunities for protein-based therapeutics.

Application of two-dimensional electrophoresis for monitoring gastrointestinal digestion of milk

Two-dimensional electrophoresis (2-DE) was used for tracing in vivo gastrointestinal digestion of milk proteins in a rapid model system with rats. Contents of stomach and small intestine from digestion trials with rats given a single dose of milk powder were recovered after 1 hour. They were then subjected to 2-DE (IEF and SDS-PAGE). 2-DE showed undigested proteins in a MW range 13.0-66.0 kDa in stomach and 13.0-25.0 kDa in the small intestine, thus indicating that milk proteins are slowly digested. This approach may shed light on pattern of protein digestion and mechanism of amino acid and peptide assimilation.

Proteolytic systems of lactic acid bacteria

Lactic acid bacteria (LAB) have a very long history of use in the manufacturing processes of fermented foods and a great deal of effort was made to investigate and manipulate the role of LAB in these processes. Today, the diverse group of LAB includes species that are among the best-studied microorganisms and proteolysis is one of the particular physiological traits of LAB of which detailed knowledge was obtained. The proteolytic system involved in casein utilization provides cells with essential amino acids during growth in milk and is also of industrial importance due to its contribution to the development of the organoleptic properties of fermented milk products. For the most extensively studied LAB, Lactococcus lactis, a model for casein proteolysis, transport, peptidolysis, and regulation thereof is now established. In addition to nutrient processing, cellular proteolysis plays a critical role in polypeptide quality control and in many regulatory circuits by keeping basal levels of regulatory proteins low and removing them when they are no longer needed. As part of the industrial processes, LAB are challenged by various stress conditions that are likely to affect metabolic activities, including proteolysis. While environmental stress responses of LAB have received increasing interest in recent years, our current knowledge on stress-related proteolysis in LAB is almost exclusively based on studies on L. lactis. This review provides the current status in the research of proteolytic systems of LAB with industrial relevance.

ACE inhibitory peptides derived from enzymatic hydrolysates of animal muscle protein: a review

Naturally occurring ACE (angiotensin converting enzyme) inhibitory peptides have a potential as antihypertensive components in functional foods or nutraceuticals. These peptides have been discovered in various food sources from plant and animal protein origin. In this paper an overview is presented of the ACE inhibitory peptides obtained by enzymatic hydrolysis of muscle protein of meat, fish, and invertebrates. Some of these peptides do not only show in vitro ACE inhibitory activity but also in vivo antihypertensive activity in spontaneously hypertensive rats. To focus on new sources of ACE inhibitory peptides, more specifically insects and other invertebrates, we compared the vertebrate and invertebrate musculature and analyzed phylogenetic relationships.

Honoring Jehovah's Witnesses' advance directives in emergencies: a response to Drs. Migden and Braen

Jehovah's Witnesses refuse blood transfusions out of obedience to the Bible's command to all Christians to abstain from blood. The Witnesses take this scriptural injunction seriously and, of their own initiative, execute advance medical directive cards to communicate their refusal to medical personnel in the event of their incapacity. In portraying the Witnesses' refusal of blood as the uninformed result of their subjugation by the Watchtower Society, Migden and Braen distort the facts about Jehovah's Witnesses, the basis for their refusal of blood, and their use of the blood refusal card. Further, not only does Migden and Braen's analysis subordinate patient values to professional preference in all cases, but the heightened scrutiny protocol they propose is useless because it cannot possibly be implemented in the hypothetical they posit. Finally, their legal analysis is not well founded and practitioners who choose to follow it will do so at their peril.