The ESD polymorphism: further studies of the ESD2 and ESD5 allele products

Purification and properties of an esterase from the yeast Saccharomyces cerevisiae and identification of the encoding gene

We purified an intracellular esterase that can function as an S-formylglutathione hydrolase from the yeast Saccharomyces cerevisiae. Its molecular mass was 40 kDa, as determined by gel filtration and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The isoelectric point was 5.0 by isoelectric focusing. The enzyme activity was optimal at 50 degrees C and pH 7.0. The corresponding gene, YJLO68C, was identified by its N-terminal amino acid sequence and is not essential for cell viability. Null mutants have reduced esterase activities and grow slowly in the presence of formaldehyde. This enzyme may be involved in the detoxification of formaldehyde, which can be metabolized to S-formylglutathione by S. cerevisiae.

Molecular analysis of esterase D polymorphism

We have analyzed the esterase D (EsD) polymorphism at the nucleic acid level. Two common alleles, EsD1 and EsD2, are characterized by the substitution of one amino acid (Gly-to-Glu), which is caused by the point mutation of one nucleotide (G-to-A). Individuals exhibiting the EsD1 and EsD 2 phenotypes are homozygotes for EsD 1 and EsD 2 cDNAs, respectively. Individuals showing the EsD 2-1 phenotype have two kinds of cDNAs, viz., EsD 1 and EsD 2. The point mutation difference between the cDNAs of the EsD1 and EsD2 alleles results in a different SspI digestion site. A restriction fragment length polymorphism caused by this difference with respect to the SspI digestion site makes it possible to determine the EsD phenotype using DNA samples extracted from forensic materials with no EsD enzymatic activity.

Electrophoretic phenotyping of erythrocyte enzymes

Erythrocyte acid phosphatase (EAP), esterase D (ESD) and phosphoglucomutase (PGM) phenotypes among the erythrocyte enzyme types of blood groups are surveyed and a modified cellulose acetate membrane isoelectric focusing (CAM-IEF) method for their exploration is described. The phenotyping procedures are usually classified as either equilibrium or non-equilibrium IEF. Equilibrium IEF, which is based on differences in pI values, includes three methods: (i) a narrow pH range of carrier ampholytes, (ii) a relatively narrow pH range of carrier ampholytes containing chemical separators and (iii) immobilized pH gradient gels. Among the three methods, immobilized pH gradients provides a better resolution of isozymes. Conversely, the disadvantages of immobilized pH gradients include longer focusing times and complex gel preparations. Moreover, immobilized pH gradients are unsuitable for stain analysis because of the insensitivity of PGM1 detection. A hybrid IEF system and a commercial immobilized pH gradient dry plate have overcome these problems. However, EAP typing is extremely expensive and ESD typing is not well distinguished by hybrid IEF. As each method has both merits and demerits, the most suitable technique should be selected based on the kind of erythrocyte enzyme types and sample conditions. On the other hand, non-equilibrium IEF is a rapid method because isozymes are detected on the basis of their charge differences under non-equilibrium conditions. Moreover, the appropriate addition separators increases the charge difference and provides a good resolution within a shorter time. Addition of more separators produces a narrow pH range in the gel and takes a substantially longer time to reach the optimum pH range for charge difference.(ABSTRACT TRUNCATED AT 250 WORDS)

Identification of human esterase D subunits from the homodimeric and heterodimeric forms of five phenotypes by a new two-dimensional isoelectric focusing method

A new two-dimensional isoelectric focusing method was developed to identify the human esterase D (EsD) subunits from the homodimeric and heterodimeric forms of five EsD phenotypes. EsD polymorphism was also analyzed by one-dimensional isoelectric focusing under reducing and mild denaturing conditions to study the influence of dithiothreitol and low concentrations of urea on the focusing pattern of the EsD dimers.

Phenotyping of erythrocyte acid phosphatase and esterase D by high field strength isoelectric focusing on cellulose acetate membrane

Phenotyping of erythrocyte acid phosphatase (EAP) and esterase D (ESD) by cellulose acetate membrane isoelectric focusing (CAM-IEF) under a nonequilibrium condition is described. In an attempt to improve the method of CAM-IEF, we shortened the electrode distance to provide a higher field strength at a given (low) voltage. Various carrier ampholytes for EAP typing and various chemical separators for ESD typing were also tested. Good separations were obtained after 30 min IEF for EAP typing and 25 min for ESD typing. When applied to blood stains and stored for various periods at room temperature, the stains up to 8 months old could still be phenotyped for EAP and those up to 4 weeks old for ESD. CAM-IEF is suitable for routine forensic work of EAP and ESD phenotyping.

Two new esterase D (ESD) variants revealed by isoelectric focusing in agarose gel

Using isoelectric focusing in thin-layer agarose gel (AGIF) with the narrow pH range of 4.5-5.4, a high resolution of esterase D (ESD) isozyme banding patterns has been achieved. Some variant phenotypes which could not be distinguished from common ESD types by conventional electrophoresis have shown different patterns after AGIF. The IEF method permitted the distinction of two further variants in the ESD system, tentatively named ESD Rehren and ESD Ravensburg. We recommend, therefore, that for the classification of ESD phenotypes a high resolution IEF technique should be used.

Purification and characterization of esterases D-1 and D-2 from human erythrocytes

Esterase D-1 (carboxylesterase; carboxylic-ester hydrolase, EC 3.1.1.1) was purified to homogeneity and esterase D-2 was highly purified from human erythrocytes. A new procedure, which included fractionation with ammonium sulfate, hydrophobic chromatography on a Toyopearl HW-65 column, and chromatographies on CM-cellulose and hydroxylapatite columns, was developed. Esterases D-1 and D-2 were purified about 9000- and 5600-fold over the precipitates with 65% saturated ammonium sulfate in 14 and 35% yields, respectively. The minimum molecular weights of esterases D-1 and D-2 were estimated to be 35,000 based on the mobilities on sodium dodecyl sulfate-polyacrylamide gel electrophoresis with or without 2-mercaptoethanol. The molecular weights of both enzymes were calculated to be 76,000 by gel filtration. These findings indicated that these two enzymes consisted of dimer without an intermolecular disulfide bond(s). Amino acid analysis of esterase D-1 showed that the total residues of aspartic acid plus asparagine, glutamic acid plus glutamine, glycine, and leucine represent about 40% of the total amino acid residues. Esterases D-1 and D-2 have almost identical biochemical characteristics, including Km values, sensitivities to sulfhydryl reagents, and molecular weights. Esterase D-2 cross-reacted with a rabbit antibody raised against the purified esterase D-1.

Effect of the esterase-D phenotype on its in vitro enzyme activity

Esterase-D phenotypes and in vitro activity have been measured in red blood cells from 258 retinoblastoma patients and 73 unaffected relatives. Individuals with the 1-1 and 2-1 phenotypes showed distributions of enzyme activity which were not significantly different from each other. Individuals with the 2-2 phenotype, however, consistently showed a 25-30% lower level of enzyme activity. These results demonstrate the importance of determining the esterase-D phenotype in individuals with low ESD activity who might otherwise be assumed to carry a chromosome deletion at the esterase-D locus. We have also shown that, in vitro, the ESD enzyme is unstable over relatively short periods of time which, if uncontrolled, can give rise to a large variation in measured enzyme levels. The addition of b-mercaptoethanol to the assay buffer, which stabilises the enzyme, results in more consistent values being obtained within the same ESD phenotype. This feature could account in part for much of the variability in enzyme activity observed between different individuals in other studies.

Identity of the polymorphisms for esterase D and S-formylglutathione hydrolase in red blood cells

The S-formylglutathione hydrolase (FGH) polymorphism of human red blood cells was studied in unrelated individuals, both by isoelectric focusing and starch gel electrophoresis, and with the substrates S-acetylglutathione and 4-methylumbelliferyl-acetate (the standard substrate for esterase D (ESD]. With both separation techniques the two substrates consistently gave similar and identically located zymograms. Thus, FGH (E.C.3.1.2.12) appears to be identical to ESD (E.C.3.1.1.1).

Esterase D typing of bloodstains by non-equilibrium focusing

Non-equilibrium focusing in a pH 4-6 gradient in ultra-thin polyacrylamide gels has been shown to be a reliable and reproducible method for detecting the six common esterase D phenotypes (EsD 1,2-1,2,5-1,5-2 and 5) in dried bloodstains. Successful typing is dependent on both the age and phenotype of the stain in question. The effects of age on the isozyme pattern of each phenotype are described and illustrated. In a comparative trial using 100 simulated and 300 authentic casework bloodstains, non-equilibrium focusing was shown to be more efficient than thin-layer starch gel electrophoresis for the typing of esterase D.

Esterase D phenotyping of bloodstains and hair roots by low voltage isoelectric focusing

A new isoelectric focusing method is described for phenotyping of esterase D in blood stains and hair roots. It permitted easy and rapid discrimination of six phenotypes determined by ESD*1, ESD*2 and ESD*7. Experiments showed it to be practicable in forensic stain work. In addition, this technique was also usable in phenotyping of ESD 5.

The use of isoelectric focusing (IEF) as a method for the combined phenotyping of erythrocyte acid phosphatase (EAP) and esterase D (EsD)

The simultaneous isoelectric focusing (IEF) in polyacrylamide gels (PAG) of erythrocyte acid phosphatase (EAP) and esterase D (EsD) allows the poor discriminating power (DP) of EsD to be usefully combined with a highly discriminating system EAP, such that a joint DP of 0.766 was achieved compared with PGM IEF DP 0.756. Focusing was carried out in a centrally flattened gradient containing ampholines (pH 4-6 and 6-8) and the chemical spacer 3-(N-morpholino) propanesulphinic acid (MOPS). It enabled the identification of six EsD phenotypes including the recently discovered EsD5 isozymes. The application of this method to casework bloodstains is discussed.

The esterase D polymorphism as revealed by isoelectric focusing in ultra-thin polyacrylamide gels

The polymorphism of human red cell esterase D (EsD) was studied using isoelectric focusing (pH 4-6) in ultra-thin polyacrylamide gels. Typing was possible without the EsD isozymes attaining true equilibrium focusing conditions. Using this single method, six phenotypes (EsD 1, 2-1, 2, 5-1, 5-2 and 5) could be recognized in the White population of south-east England. Family studies showed these to be controlled by three co-dominant alleles and the gene frequencies were calculated to be EsD1 0.8856; EsD2 0.0946 and EsD5 0.0198. For successful and reliable EsD typing by this method, the electrophoretic system must be carefully optimized with respect to the duration of electrophoresis and the temperature attained in the gel during the electrophoretic run.

Population genetic studies in three Chinese minorities

Three minority ethnic groups from China (Mongolians, Koreans, Zhuang) were examined with respect to the genetic markers GLO, GPT, ACP, ESD, 6-PGD, PGM1 subtypes, C3, and TF. Significant variations were noted for the gene frequencies of GLO, GPT, ESD, sub PGM1 between Zhuang and Mongolians; for GPT, ACP, ESD, sub PGM1 between Zhuang and Koreans; and for GLO between Mongolians and Koreans.

A method to increase the volume of sample applied to isoelectric focusing gels

Isoelectric focusing of extracts from diluted or aged bloodstains may be more successfully accomplished with larger sample volumes applied to the gel. A technique is described using teflon tubing to apply larger sample volumes (up to 100 microliters) to isoelectric focusing (IEF) gels. This method is reproducible and easy to perform.

Isoelectric focusing studies of human red cell esterase D: evidence for polymorphic occurrence of a new allele EsD7 in Japanese

The isoelectric focusing study of esterase D in Japanese revealed evidence of a new polymorphic allele (EsD7) which is difficult to find by conventional starch gel electrophoresis only. A comparison with the occurrence of a subdivision of EsD2 in Caucasians (EsD5) suggests a remarkable difference in allele distribution of esterase D among races. Quantitative analysis showed a relatively low value of enzyme activity for this new allele. It is therefore emphasized that in addition to conventional electrophoresis, enzyme assay and further detection by isoelectric focusing are essential in analyzing the esterase D system.

Review of isoelectric focusing for Gc, PGM1, Tf, and Pi subtypes: population distributions

Isoelectric focusing (IEF) as a method for differentiating macromolecules with minor differences in isoelectric points has demonstrated an increase in the degree of genetic polymorphisms of the blood. Studies over the last 5 to 6 years have shown that genetic marker systems such as transferrin (TF), phosphoglucomutase (PGM1), the vitamin D-binding globulin (GC), and A1 antitrypsin (PI) are a great deal more polymorphic than observed using conventional electrophoresis. Additional genetic variants have been detected or further defined in such systems as esterase D (ESD) and hemoglobin (HB) to name a few. The increased heterozygosity levels of these genetic marker systems identified by IEF have added to their value in forensic medicine and resulted in further resolution of racial and population affinities. IEF should prove to be a valuable anthropological tool for measuring population structure and genetic distances.