Constitutive Enzymes

The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Constitutive Enzymes

 

enzymes that are present in cells at all times (in contrast to induced enzymes, whose synthesis depends on the adaptation of the organism to a specific substrate).

The terms “constitutive enzyme” and “induced enzyme” were initially applied to bacterial enzymes whose biosynthesis was studied in relation to the composition of the nutrient medium, or substrate. The two types differ quantitatively rather than qualitatively: most induced enzymes are formed in insignificant quantities without the addition of an inducer, whereas the amount of many constitutive enzymes increases when the specific substrate is added. Induced enzymes can become constitutive by mutation (for example, a mutant was found in E. coli that produced the induced enzyme β-galactosidase in the total absence of an inducer). Crystalline preparations of the enzyme, formed both inductively and constitutively (in a mutant), are identical in all respects. According to the unitary theory, both classes of enzymes are formed by the same mechanism as a result of induction, but only in constitutive enzymes do normal metabolites function as inducers.

REFERENCE

Dixon, M., and E. Webb. Fermenty. Moscow, 1966. (Translated from English.)
The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
Constitutive enzymes generate a small amount of NO, while the activity of iNOS is approximately one thousand times higher [2].
The MLEE method used was as previously described (8-10); the electrophoretic mobility of 15 constitutive enzymes was analyzed.
Although some are constitutive enzymes, results may imply that the enzymatic systems ADH, MDH, ME and PGI at 14 DAT, and EST and ME at 28 DAT are more expressed and that japonica cultivars have more intense bands in proportion to increasing salinity.
Since it is a constitutive enzyme, MDH is important because it shows activity in all evaluated cultivars and sampling periods.
Some sources are of Primary utilization by fungi, and are converted to Intracellular ammonia by constitutive enzymes, While others need gene induction and enzyme Synthesis before utilization (Pereira et al., 2003; Tudzynski, 2014).