Synthetic substrate analogues

Smith TK, Sharma DK, Grossman A et al. Parasite and mammalian GPl biosynthetic pathways can be distinguished using synthetic substrate analogues. EMBO J 1997 16 6667-6675. 

Substrate specificity of SLO-1 has been studied using as synthetic substrate analogues an entire series of dienoic acid and dienols, i.e. (co-6Z,(0-9Z)-Ci3 C20-dienoic acids and (o -6Z,(o-9Z)-Ci2 C20-dienoic [260]. The highest relative activity is observed with... 

F. Reck, M. Springer, E. Meinjohanns, H. Paulsen, I. Brockhausen, H. Schachter, Synthetic substrate analogues for UDP-GlcNAc Man alpha 1-3R beta 1-2-N-acetylglucosaminyl-transferase I. Substrate specificity and inhibitors for the enzyme, Glycoconj J, 1995, 12, 747-754. 

In vitro and ex vivo studies have shown that FATPs transport LCFAs and very long-chain fatty acids (VLCFAs) but no medium-chain fatty acids, fatty acid esters, or lipid-soluble vitamins [4]. LCFA transport is inhibited by prior protease treatment. Synthetic substrates for FATPs include 14C-labeled fatty acids and the fluorescently labeled fatty acid analogue C1 -BODEP Y-Cl 2. Using the latter substrate, differences in fatty acid uptake kinetics between FATP expressing 3T3 LI adipocytes and 3T3 LI fibroblasts, which are devoid of FATPs, can be readily appreciated (Fig. 2). 

A substrate analogue is a synthetic (rather than natural) compound that can act as a substrate for a particular enzyme. 

Substrate analogues containing the mercaptan functionaUty have been extensively investigated as collagenase inhibitors, and some other sulphur-based functionalities have also been explored [1,161,172-185]. The mercap-tans tend to be very potent inhibitors of all of the MMP, presumably due to the strong interaction between the active site Zn(II) and the mercaptide anion. Unfortunately, these compounds tend to undergo inactivation by oxidative disulphide formation. However, the rate at which this occurs varies widely and depends on the structure of the inhibitor. The most common synthetic route to these derivatives again leads to a diastereomeric mixture. 

Five- to six-month-old tobacco plants (Nicotiana tabacum var. Samsun) grown in a glasshouse at 20°C were used for this study. Commercial synthetic substrates employed both for histochemical and biochemical assays were guaiacol, p-phenylenediamine-pyrocatechol (PPD-PC), 3-3 di-aminobenzidine (DAB), tetramethylbenzidine (TMB) and syringaldazine. Isopropylamine and monosodium salts of ferulic acid were also used as substrates as well as their / -fluorinated analogues substituted with a fluorine atom on the / -carbon (Fig. 1). Histochemical observations were done on hand-made transverse sections of fresh tobacco stems. Biochemical assays were performed separately on bark (inner cortical parenchyma, phloem and fibres) and xylem fractions. Technical data of incubation, enzyme extraction, spectrophotometric and electrophoretic assays were given elsewhere (5-7). Synthesis of fluorinated compounds was performed as previously described (4). 

Figure 6 Substrate analogues of the Fpg protein. The synthetic derivatives of oxidized guanine (7, 8, 9, 10J and abasic site analogues (11, 12, 13, 14 are high affinity ligands for Fpg. Chemical "mutations" of natural damages are indicated by red atoms.

Essential characteristics of synthetic enzyme analogues are summarized in the Box on page 460. Many of these features are closely interrelated, such as complexation, saturation kinetics, and substrate selectivity, as well as competitive inhibition by stronger binding substrates, which are less reactive or completely unreactive. Regio- or stereoselectivity, if applicable, can change in comparison to the uncatalyzed process by a variation in structure or by disposition of the transition state, for example, from early to late or from an SN1 to an Sn2 mechanism. 

Initial attempts to develop aromatase inhibitors for use in the treatment of oestrogen-dependent breast cancer involved the use of synthetic steroid analogues of the natural substrates androstenedione and testosterone [53]. Such steroidal inhibitors are reviewed in on p. 272. An alternative approach to the design of aromatase inhibitors was suggested by the discovery [54-56]... 

The enzyme 5-oxo-L-prolinase which catalyses the conversion of 5-oxo-L-proline to L-glutamate coupled to the consumption of ATP (Fig. 33.38), was shown by Williamson and Meister to also act on a synthetic substrate, L-2-oxothiazolidine-4-carboxylate, which is an analogue of 5-oxoproline with the 4-methylene group replaced by sulphur. 

---