at Related Biological Terms

Muscle that on microscopic examination shows a banding pattern that is due to the regular spacing of areas of overlap of thick and thin filaments within each sarcomere; includes skeletal muscle and cardiac muscle.

A data set that is the product of screening a potential drug to indicate which of its atoms contribute to its effect. (see also AT queue)

A reactant in an enzymic reaction.

(see entropy effect)

The sequential action of a multienzyme complex upon a substrate that prevents the dissociation of intermediate products.

(= futile cycle (substrate cycle))

Substrate inhibition is the inhibition of an enzymic reaction at high substrate levels, usually due to a second, inhibitory, and lower-affinity binding site for the substrate in addition to the catalytic site. Substrate inhibition is the most common deviation from Michaelis–Menten kinetics, occurring in approximately 25% of known enzymes. It is generally attributed to forming an unproductive enzyme-substrate complex after the simultaneous binding of two or more substrate molecules to the active site. Substrate concentration affects the primary rate and yield of enzymatic hydrolysis. High substrate concentrations can result in substrate inhibition, significantly lowering the hydrolysis rate. Problems relating to heat and mass transfer efficiency reduction, rheological issues, and increased inhibitor concentration have been reported associated with high solid loading. The substrate inhibits the microbial growth rate at high substrate concentrations. As in enzyme kinetics, substrate inhibition of growth may be competitive or noncompetitive. Suppose a single-substrate enzyme-catalyzed reaction is a rate-limiting step in microbial growth. In that case, the inhibition of the enzyme activity results in the inhibition of microbial growth by the same pattern.

A method for identification of the substrate specificity of a proteinase by its ability to select a phage that expresses a cleaveable polypeptide, which is one of a library of random amino acid sequences fused to a protein that tethers the phage to a solid support. Selection of the phage is by cleavage of the polypeptide. Several cycles of binding, proteolysis and phage propagation select the phage that expresses the scissile bond. Matthews, D.J. and Wells, J.A. (1993) Science 260, 1113-1117

The metabolic synthesis of ATP that does not require the electron transport chain, e.g. the glyceraldehyde-3-phosphate dehydrogenase reaction.

A variation of subtractive DNA cloning in which the restriction-nuclease-cleaved tester DNA is biotinylated before annealing with an excess of randomly sheared driver DNA. Annealing is halted at about 90% completion and the single-stranded DNA is separated from double-stranded DNA. As the unique tester fragments are present at lowest concentration, they will be slowest to find complementary strands and anneal and will, therefore, be enriched in the remaining single-stranded DNA fraction. They are isolated on the basis of biotin's affinity for immobilized avidin and subjected to subsequent cycles of purification. Wieland, I., Bolger, B., Asouline, G. and Wigler, M. (1990) Proc. Natl. Acad. Sci. U.S.A. 87, 2720-2724