Photoregulation of an Enzymic Process by Means of a Light-Sensitive Ligand

Abstract

A specific inactivator of chymotrypsin, p-azophenyldiphenylcarbamyl chloride, exists as two geometric isomers, cis and trans, which are interconvertible by means of light. The cis-isomer is five times more reactive than the more stable trans-isomer, and is obtained by exposure of the latter to light of 320 nanometer wavelength. The trans-isomer can be regained by exposure of the cis-isomer to light of 420 nanometer wavelength. This interconversion can be made to occur in aqueous solution in the presence of the enzyme under conditions in which the trans-isomer reacts relatively slowly with chymotrypsin. Thus, it is possible to regulate the rate of inactivation of chymotrypsin by using light of the appropriate wavelength. This system is presented as a model for some of the light-sensitive metabolic systems present in living organisms.

Artificial Light‐sensitive Enzymatic Systems as Chemical Amplifiers of Weak Light Signals

“…Its photochromic azoderivative (II), N-p-phenylazophenyl-N-phenylcarbamyl chloride, can exist in trans-and cis-configurations. The equilibrium between the two forms may be shifted by illuminating I1 with light of a certain wavelength (Kaufman et al, 1968):…”

“…It turned out (Kaufman et al, 1968) that cis-I1 inactivates a-chymotrypsin five times as fast as trans-11. Approximately the same differences in the rates of inactivation under the action of stereoisomers I1 (and also two other related compounds) were reported for acetylcholinesterase (Bieth et al, 1969 and1973).…”

Photoregulation of Biological Activity by Photocromic Reagents, Ii. Inhibitors of Acetylcholinesterase

“…1 The photosensitive compound, N-p-phenylazophenyl-N-phenylcarbamyl chloride2 (PAPC), is a specific inactivator of chymotrypsin.3 PAPC is a photochromic (or phototropic) molecule4 which, under the influence of light, can undergo a reversible configurational change involving the N = N bond, to yield either a cis or a trans isomer. The change in structure is influenced by the wavelength of light as follows: 320 nm trans = cis 420 nm Although both isomers could inactivate chymotrypsin, the cis isomer was found to be about five times more active.…”

Interaction of alpha-Chymotrypsin with N-Cinnamoylimidazole. Substrate Sensitive to Light

“…These stereoisomeric acylenzymes are interconvertible by means of light. Erlanger et al [2] found that it is possible to regulate the rate of interaction of chymotrypsin with p-azophenyldiphenylcarbamyl chloride by using light of the appropriate wavelength (the cis-isomer is five times as reactive as the more stable trans-isomer). The two systems [1,2] can be considered as models for some of the light-sensitive metabolic processes present in living organisms (cf.…”

“…The two systems [1,2] can be considered as models for some of the light-sensitive metabolic processes present in living organisms (cf. [2]). Furthermore, it should be pointed out that light-regulated cis-trans isomerism is a part of the mechanism of vision [1,3].…”