Variation in enzyme structure and function: the guidelines of evolution

Mimicomes: Mimicking Multienzyme System by Artificial Design

Enzymes are widely distributed in organelles of cells, which are capable of carrying out specific catalytic reactions. In general, several enzymes collaborate to facilitate complex reactions and engage in vital biochemical processes within cells, which are also called cascade systems. The cascade systems are highly efficient, and their dysfunction is associated with a multitude of endogenous diseases. The advent of nanotechnology makes it possible to mimic these cascade systems in nature and realize partial functions of natural biological processes both in vitro and in vivo. To emphasize the significance of artificial cascade systems, mimicomes is first proposed, a new concept that refers to the artificial cascade catalytic systems. Typically, mimicomes are able to mimic specific natural biochemical catalytic processes or facilitate the overall catalytic efficiency of cascade systems. Subsequently, the evolution and development of different types of mimicomes in recent decades are elucidated exhaustedly, from the natural enzyme-based mimicomes (immobilized enzyme and vesicle mimicomes) to the nanozyme-based mimicomes and enzyme-nanozyme hybrid mimicomes. In conclusion, the remaining challenges in the design of multifunctional mimicomes and their potential applications are summarized, offering insights into their future prospects.

Evolution of phosphagen kinase V. cDNA-derived amino acid sequences of two molluscan arginine kinases from the chiton Liolophura japonica and the turbanshell Battilus cornutus

The cDNAs of arginine kinases from the chiton Liolophura japonica (Polyplacophora) and the turbanshell Battilus cornutus (Gastropoda) were amplified by polymerase chain reaction (PCR), and the complete nucleotide sequences of 1669 and 1624 bp, respectively, were determined. The open reading frame for Liolophura arginine kinase is 1050 nucleotides in length and encodes a protein with 349 amino acid residues, and that for Battilus is 1077 nucleotides and 358 residues. The validity of the cDNA-derived amino acid sequence was supported by chemical sequencing of internal tryptic peptides. The molecular masses were calculated to be 39,057 and 39,795 Da, respectively. The amino acid sequence of Liolophura arginine kinase showed 65-68% identity with those of Battilus and Nordotis (abalone) arginine kinases, and the homology between Battilus and Nordotis was 79%. Molluscan arginine kinases also show lower, but significant homology (38-43%) with rabbit creatine kinase. The sequences of arginine kinases could be used as a molecular clock to elucidate the phylogeny of Mollusca, one of the most diverse animal phyla.

Nongenetic variation, genetic-environmental interactions and altered gene expression. II. Disease, parasite and pollution effects

The use of protein electrophoretic data for determining the relationships among species or populations is widespread and generally accepted. However, there are many confounding factors that may alter the results of an electrophoretic study and may possibly allow erroneous conclusions to be drawn in taxonomic, systematic or population studies. Measured enzyme activities can also be affected significantly. Parasites, disease and pollution can affect levels of enzyme activity, and electrophoretic results can be affected both quantitatively and qualitatively. Blood serum is particularly vulnerable to variation to variation due to disease, pollution or parasites because damaged tissues may release tissue-specific enzymes into the bloodstream. Capture, handling, chemical treatments, bacteria, natural toxins and consumed food may also contribute to variation. Potential pollution impacts at specimen collection sites should be investigated, and study organisms should be inspected and/or treated for detection and elimination of parasites and disease.

Nongenetic variation, genetic-environmental interactions and altered gene expression. I. Temperature, photoperiod, diet, pH and sex-related effects

The use of protein electrophoretic data for determining the relationships among species or populations is widespread and generally accepted. However, many confounding factors may alter the results of an electrophoretic study in such a way as to allow erroneous conclusions to be drawn in taxonomic, systematic or population studies. Such variables as temperature, photoperiod, salinity, pH and diet have been shown to influence enzymes and proteins both quantitatively and qualitatively. Production of distinct "cold" and "warm" isozymes or "seasonal" isozymes have been found in a variety of organisms. The factors that are or may be responsible for the appearance of these isozymes is discussed. Most studies that have demonstrated some apparent form of environmentally induced genetic expression have not determined that mechanisms responsible. However, proteolytic modification has been shown to produce seasonal isozymes of fructose 1,6-bisphosphatase in rabbit liver and may account for other seasonal isozymes. Acclimating organisms to various conditions may actually allow detection of cryptic genetic variation and provide valuable data. There are many aspects to consider in designing acclimation experiments, and the conditions used will vary according to the aim of the research. Polyploidy may contribute to the genesis of environmentally regulated isozymes. A review of this literature follows with additional hypotheses and conclusions. Recommendations are given for the resolution of real and potential problems.

Properties and reaction with iodoacetamide of adenosine 5'-triphosphate-creatine phosphotransferase from human skeletal muscle. Further evidence about the role of the essential thiol group in relation to the mechanism of action

1. The purification of creatine kinase from human and monkey skeletal muscle by horizontal electrophoresis on Sephadex blocks is described. 2. The purified enzymes are shown to have similar chemical and kinetic properties to the rabbit muscle enzyme and a common mechanism is inferred. 3. Iodoacetamide has a similar apparent second-order inhibition constant with the human and rabbit enzymes, but the inhibition does not go to completion with the former. This is even more marked with the monkey enzyme, which has more reactive thiol groups, but inhibition is only about 50%. 4. Single substrates have little effect on the inhibition by iodoacetamide, but with the primate enzymes, in contrast with the rabbit enzyme, high concentrations of ADP-Mg(2+) plus creatine convert the essential thiol group from being pH-independent into one with a normal ionization. Low concentrations of ADP-Mg(2+) plus creatine first enhance the rate of inactivation, but cause protection as the reaction proceeds. These results are interpreted to indicate an activation of the thiol group on the subunit to which the substrates bind and a co-operatively induced decrease in the activity of the thiol group on the other subunit which lacks substrates. 5. The effects of a substrate equilibrium mixture on the rate of inhibition are essentially those of ADP-Mg(2+) plus creatine. 6. Since no substrate combination affords significant protection to the thiol group associated with the catalytic site to which the substrates are bound, it is concluded that any mechanism involving the thiol group in a direct participation in the transition-state complex of the catalytic reaction must be abandoned unless the transition state is only a small part of the time taken for one catalytic cycle.