We have surveyed proteins with known atomic structure whose function involves electron transfer; in these, electrons can travel up to 14 A between redox centres through the protein medium. Transfer over longer distances always involves a chain of cofactors. This redox centre proximity alone is sufficient to allow tunnelling of electrons at rates far faster than the substrate redox reactions it supports. Consequently, there has been no necessity for proteins to evolve optimized routes between redox centres. Instead, simple geometry enables rapid tunnelling to high-energy intermediate states. This greatly simplifies any analysis of redox protein mechanisms and challenges the need to postulate mechanisms of superexchange through redox centres or the maintenance of charge neutrality when investigating electron-transfer reactions. Such tunnelling also allows sequential electron transfer in catalytic sites to surmount radical transition states without involving the movement of hydride ions, as is generally assumed. The 14 A or less spacing of redox centres provides highly robust engineering for electron transfer, and may reflect selection against designs that have proved more vulnerable to mutations during the course of evolution.

Natural engineering principles of electron tunnelling in biological oxidation-reduction.

�Microprocessor-controlled changes of [free Ca 2 '] at the outer surface of the Sarcoplasmic reticulum (SR) wrapped around individual myofibrils of a skinned canine cardiac Purkinje cell and aequorin bioluminescence recording were used to study the mechanism of Ca 2 '-induced release of Ca 21 from the SR . This Ca2' release is triggered by a rapid increase of [free Ca 21] at the outersurface of the SR of a previously quiescent skinned cell . Ca 2 '-induced

Calcium-induced Release of Calcium from the Sarcoplasmic Reticulum of a Skinned Canine Cardiac Purkinje Cell

3Core Research for Evolutional Science and Technology (CREST), Chiyoda-ku, Tokyo, 101-0062 Japan ; Class III plant peroxidase (POX), a plant-specific oxidoreductase, is one of the many types of peroxidases that are widely distributed in animals, plants and microorganisms. POXs exist as isoenzymes in individual plant species, and each isoenzyme has variable amino acid sequences and shows diverse expression profiles, suggesting their involvement in various physiological processes. Indeed, studies have provided evidence that POXs participate in lignification, suberization, auxin catabolism, wound healing and defense against pathogen infection. Little, however, is known about the signal transduction for inducing expression of the pox genes. Recent studies have provided information on the regulatory mechanisms of wound- and pathogen-induced expression of some pox genes. These studies suggest that pox genes are induced via different signal transduction pathways from those of other known defense-related genes.

/pdf/a-large-family-of-class-iii-plant-peroxidases-1plxqcbkk0.pdf

A large family of class III plant peroxidases.

https://acsjournals.onlinelibrary.wiley.com/doi/epdf/10.1002/1097-0142%28195803/04%2911%3A2%3C283%3A%3AAID-CNCR2820110209%3E3.0.CO%3B2-8

The colorimetric determination of leucine aminopeptidase in urine and serum of normal subjects and patients with cancer and other diseases.

Methylglyoxal in living organisms: chemistry, biochemistry, toxicology and biological implications.

The Enzymes, Chemistry and Mechanism of Action

Group transfer, syntheses coupled to ATP cleavage

Prosthetic groups and cofactors (part B)

Hydrolytic cleavage (part B) : phosphate ester cleavage, acid anhydride cleavage, phosphorolytic cleavage, C-C synthesis and cleavage, isomerization, hydration and dehydration

Karl Myrbäck

Papers

The Enzymes, Chemistry and Mechanism of Action

Group transfer, syntheses coupled to ATP cleavage

Prosthetic groups and cofactors (part B)

Hydrolytic cleavage (part B) : phosphate ester cleavage, acid anhydride cleavage, phosphorolytic cleavage, C-C synthesis and cleavage, isomerization, hydration and dehydration