ESTERASE VARIATION IN TURKISH WHITE-TOOTHED SHREWS (CROCIDURA): RECORD OF A TRIMERIC ESTERASE

This study focuses on esterase variation of the genus Crocidura in Turkey. A total of 248 white-toothed shrews were analyzed by means of cellulose acetate gel electrophoresis. Liver tissue and alfa naphthyl acetate were used to investigate esterase variation in Turkish white-toothed shrews. A different esterase banding pattern was found in one Crocidura individual. This phenotype had four anodally migrated bands on cellulose acetate gel. The Crocidura individual displaying the given phenotype was identified as Crocidura suaveolens. The different esterase banding pattern observed in this study is considered to be a result of the trimeric structure of esterase in the lesser white-toothed shrew (Crocidura suaveolens).


INTRODUCTION
Living organisms have a great number of enzymes, which are extremely large biomolecules important for metabolic events and polymorphism in organisms (Bugg, 2004).Enzymes may often possess subunit structures such as monomers, dimers, trimers, and tetramers in animals and other organisms.Of these subunit structures, the trimeric structure has not been extensively reported in vertebrates, including mammals (Richardson et al., 1986;Manchenko, 2003).
The enzyme esterase (EST) (EC 3.1.1.1),known as an important hydrolase enzyme in animals (Bugg, 2004), is polymorphic and generally composed of one or two subunits (Richardson et al., 1986;Hoelzel, 1998;Manchenko, 2003).It was reported by Kendal (1983) that the esterases are characterized by substrate specification, tissue distribution, and electrophoretic mobility.The enzyme esterase was found to be trimeric in some organisms, including man, rat, pig, guinea pig, and the common shrew (Hopkinson et al., 1976;Heymann, 1980;Oehm et al., 1982;Searle, 1986).So far, there are no data available indicating the existence of trimeric forms in white-toothed shrews.
In the present study, we investigated whether or not esterase variation exists in the Turkish whitetoothed shrews.

MATERIAL AND METHODS
A total of 248 Crocidura samples collected from Turkey were examined for esterase variations.The samples of Crocidura were captured from the field

ESTERASE VARIATION IN TURKISH WHITE-TOOTHED SHREWS (CROCIDURA):
RECORD OF A TRIMERIC ESTERASE with mouse traps and were humanely killed in the field and/or the laboratory.Liver tissues were used for enzyme electrophoresis.Such tissues were sampled from freshly killed white-toothed shrews (Crocidura).All tissues were washed thoroughly in physiological saline (0.9% NaCl) (Searle, 1986) and frozen on dry ice in the field or at -80 o C in the laboratory.Tissues frozen in the field were transferred to -80 o C. With these tissues, tissue homogenization, enzyme electrophoresis, and staining for esterase were performed according to the method published by Richardson et al. (1986).The samples of liver tissue were run on cellulose acetate plates (94x76-and 60x76-mm Titan III plates, Helena Lab) in a cooled electrophoresis unit.

RESULTS
Esterase variation of Crocidura samples collected from Turkey was investigated by means of cellulose acetate gel electrophoresis, alfa naphthyl acetate being used to stain samples of liver homogenates.
All samples migrated anodally on cellulose acetate gels.Of 248 samples, only one, which was collected from Samsun in the Black Sea region of Turkey, displayed a different banding pattern for esterase.This individual was recognized as Crocidura suaveolens according to Tez (2000) and Krystufek and Vohralik (2001).The phenotype observed in C. suaveolens was with four bands that migrated anodally on the gel (sample 583, Fig. 1).The remaining 247 Crocidura samples screened were observed to have a single band.
Mouse, rat, guinea pig, pig, and man are not soricids.However, the common shrew, Sorex araneus, is a soricid, as is white-toothed shrew (Crocidura).Searle's study (1986) is of interest to us because he reported that the enzyme esterase has six phenotypes in Sorex araneus.Searle found that esterase in Sorex areneus is trimeric in regard to its subunit numbers.Heymann (1980) reported a trimeric structure of esterase in human, pig, rat, and guinea pig liver, as well as pig kidney.Searle (1986) used the kidney of common shrews and alfa-naphthyl propionate as substrate.We used the liver of white-toothed shrews and alfa naphthyl acetate.Up to now, a trimeric esterase has not been reported in soricids, except by Searle (1986).In the present study, the quaternary structure of esterase in one Crocidura sample identified as C. suaveolens (like Sorex araneus, a member of the family Soricidae) may be a trimeric structure.This result is in keeping with results on S. araneus from Britain reported by Searle (1986).Thus, a trimeric structure arose in different substrates and tissues.As stated by Searle (1986), "this trimeric structure may be an ancient character belonging to mammals".

Fig. 1 .
Fig. 1.Photograph of a cellulose acetate gel showing two different phenotypes (single band and four bands) of esterase in Turkish Crocidura.