Protein extrusion reactions

Protein extrusion reactions are effective only when the protein active site constitutes an integral substructure as that which occurs in the iron-sulfur proteins with Fe S core and in heme iron proteins where it is possible to extrude the iron-protoporphyrin IX prosthetic group. 

Chemical Reactions Occurring in Proteins During Extrusion... 

During extrusion, general browning typified by carameli-zation, Maillard, and oxidative decomposition reactions are paramount in flavor compound formation. Temperature and shear conditions occurring during extrusion can provide the chemical and physical means whereby complex starch and protein can be partially degraded to provide reactants that can then participate in browning. 

By thermal and shear forces during extrusion which cause protein rearrangement/degradation, the Maillard reaction progresses, and a wide variety of potent flavoring compounds can result. Reaction rates in turn are influenced by the types of sugars and amino acids present, temperature, water activity, duration of heating, and pH. 

Early biological effects Initial reactions towards the presence of contaminants Defence mechanisms are a special case of early biological effects. They are either adaptive or defensive reactions and do not represent actual toxic damage. Extrusion of chemicals outside cells by protein pumps Induction of metal-binding proteins or biotransformation enzymes for elimination... 

The most important reactions of synthetic Fe-S clusters are electron transfer and ligand substitution. The latter reaction forms the basis of the core extrusion method (66), useful for identifying certain clusters present in proteins, and allows the introduction of diverse chemical environments around the Fe-S cluster. We begin our consideration of subsite properties by summarizing the environments thus far achieved synthetically in [4Fe-4S] clusters. 

Stanley, D.W. Protein reactions during extrusion processing. Extrusion Cooking C. Mercier, P. Linko, J.M. Harper, Eds. American Association of Cereal Chemists, Inc. St. Paul, MN, 1989 pp. 321-341. 

Since the soluble fraction and the endoplasmic reticulum seem to be closely related, the mechanism of transfer of the product of a reaction catalyzed in one cell fraction to the other cell fraction may be a simple one. It is also possible that the endoplasmic reticulum separates pools of soluble protein, each containing its own battery of enzymes. Under such conditions, the products of the reaction catalyzed in the endoplasmic reticulum could conceivably be directed into alternative metabolic pathways. A mechanism by which the intracellular distribution of the enzyme controls cellular metabolism may be the selection of a given pathway on the basis of cell need. The transfer of the product of enzyme reactions associated with the endoplasmic reticulum to mitochondria (L-xylose) must be followed by extrusion from the mitochondria of the final product of xylose metabolism, D-xylose-5-phosphate, if the glucuronic pathway is to be complete. The mechanism that controls the passage of these metabolites through the mitochondrial membrane is most intriguing. Knowledge of this mechanism would probably provide new clues on metabolic controls. 

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