305

Biochem. J. (1992) 282, 305-308 (Printed in Great Britain)

Kfl4

LETTER

iJ

Nomenclature for human glutathione transferases The nomenclature for the glutathione transferases has been a subject of discussion and concern for investigators in the field. We are proposing a unifying nomenclature for the human transferases based on the following guidelines. (1) Each naturally occurring subunit encoded by a discrete gene should have its own designation. (2) The subunits should be grouped into recognized classes or gene families of glutathione transferase and be numbered sequentially within the class, using Arabic numerals, in the order that they are described. So far, four classes of soluble enzymes have been identified: Alpha, Mu, Pi, and Theta; as well as one microsomal enzyme. (3) New glutathione transferases should be included in the nomenclature system only when their complete primary structures are known unambiguously. (4) The designation of an enzyme should reflect its subunit composition. A hyphen is used to separate the symbols for the subunits of an enzyme. (5) Subunits encoded by the same gene locus should be designated by the same Arabic numeral; allelic variants will normally be distinguished by letters. The new nomenclature system proposed relates the different forms of soluble glutathione transferase to the classes Alpha, Mu, Pi, and Theta (Table 1). The letter designation of the enzymes (A, M, P and T) shows their assignments to one of these classes. The available information based on all known mammalian glutathione transferases suggests that the overall amino acid sequence identities between any two members within a class is > 50 °/. In naming individual enzymes, Arabic numerals showing the subunit composition are used and the subunits named in the order that they are described and characterized within a given class. No change in the nomenclature of the

microsomal enzyme is proposed, since this protein is clearly not a member of the supergene family of the soluble glutathione transferases; however, the enzyme is included in Table 1 for completeness. Roman letters and Arabic numerals are used in concordance with the conventions for naming gene loci; superscripts, subscripts and Greek letters are not acceptable. This rule has been adopted by geneticists for gene designations in order to provide a clear and consistent system, and to facilitate type-setting and work on computers [1]. Thus, the major basic glutathione transferase (c, B1Bl, GSTl-l, GST2-type 1 or axxx) originally described in human liver will be called human glutathione transferase Alpha l-1, abbreviated GSTAl- 1. The corresponding gene locus will be denoted GSTA1. A second homodimeric class Alpha enzyme (y, B2B2, GST2-2, GST2-type 2 or ayay) is designated as glutathione transferase Alpha2-2 or GSTA2-2, and the heterodimeric protein previously referred to as glutathione transferase a or B1B2 or GST2-type 2-1 is now referred to as glutathione transferase Alphal-2 or GSTAI-2. Human glutathione transferases ,u and V are generally considered to be allelic variants encoded at the same gene locus and will therefore both be designated as human glutathione transferase Mul-1. Allelic enzyme forms will be distinguished by lower case letters (a,b,...) indicating the type under consideration. Thus, glutathione transferase It or GST1-type 2 will be referred to as GSTMla-la and glutathione transferase if or GSTl-type 1 will be referred to as GSTMlb-lb (Table 1). The corresponding hybrid form GSTu/lf or GSTI-type 2-1 will be referred to as GSTMla-lb. In the gene designations for allelic variants, the allelic characters are separated from the locus characters by an asterisk. A null allele is denoted 0 (capital letter 0) (Table 2), or QO when no quantity of the gene product is detectable.

Table 1. Nomenclature for human glutathione transferases (GSTs)

Sequence information for the GST subunits listed and named is available in the references cited. A compilation of amino acid sequences as well as some physicochemical and enzymic properties is available [2]; additional data are obtainable in recent volumes on glutathione transferases [3,4]. Proteins

Genes

Previous

New

designation as GST

Class

designation

BlBl,GST2-type 1, H.(subunit 1), a.a. y, B2B2, GST2-type 2, Ha(subunit 2), xyay

Alpha Alpha

GSTA1-1 GSTA2-2 GSTM la-la GSTM lb-lb GSTM2-2 GSTM3-3 GSTP1- 1

c,

It, GSTI-type 2, Hb(subunit 4)

#Y, GST1-type 1 Muscle, GST4 Brain, GST5 m7, GST3

GSTO

Mu Mu Mu Mu Pi*

Thetat

Locus

Reference

designation

Chromosome

Reference

[5-7]

GSTAI

[7,8]

GSTA2

6 6

[10] [1 1] [12] [13,14] [16] [17]

GSTMJ GSTMJ

it it

[6] [6]

GSTM2 GSTM3 GSTPI

[9]

11

[9] [9] [15]

12 [18] GST12 Microsomal Microsomal GST * At least two allelic variants of GSTP1 have been identified [13-15], but the full length cDNA sequence of only one allele has been published. t Available amino acid sequence data demonstrate unambiguously the existence of a distinct class named Theta [16]; designation of individual enzymes will be made when full length sequences become known. t A recent paper [19] has questioned the original chromosome assignment for GSTMI.

Vol. 282

BJ Letters

306 Table 2. Example of relationships between designations of enzymes, phenotypes, alleles and genotypes for a human class Mu glutathione transferase (GST)

2. Enzyme

Phenotype

GSTM la-la

GSTM 1 A

GSTM1a-lb

GSTM 1 A,B GSTM 1 B

GSTMlb-lb

GSTM I null

Allele

Genotype(s)

GSTMJ*A GSTMJ*A/GSTMJ*A GSTMI*A/GSTMI*O

3. 4.

GSTMJ*A/GSTMJ*B

5.

GSTMJ*B GSTMJ*B/GSTMJ*B GSTMJ*B/GSTMJ*O GSTMJ*O GSTMJ*O/GSTMJ*O

6.

This system for naming glutathione transferases can easily be extended to other mammalian species. When it is necessary to distinguish enzymes from different species, the designation could be prefixed with a lower case letter showing its origins. Thus, the human and rat class Pi glutathione transferases may be distinguished as hGSTP1- 1 and rGSTPl- 1. A more complete prefix for species identification should be based on Latin names as adopted for homologous genes, e.g. HSA for Homo sapiens, RNO for Rattus norvegicus or MMU for Mus musculus [1]. The authors of this paper will serve as a consulting group and assist in naming new enzyme forms that may be discovered.

Bengt MANNERVIK*, Yogesh C. AWASTHIt, Philip G. BOARDt, John D. HAYES§, Carmine DI ILIOII, Brian KETTERER¶, Irving LISTOWSKY**, Ralf MORGENSTERNtt, Masami MURAMATSUtt, William R. PEARSON§§, Cecil B. PICKETTIII", Kiyomi SATO¶¶, Mikael WIDERSTEN* and C. Roland WOLF*** *Department of Biochemistry, Biomedical Center, Uppsala University, Box 576, S-751 23 Uppsala, Sweden tDepartment of Human Biological Chemistry and Genetics, University of Texas Medical Branch, Galveston, TX 77550, U.S.A. tMolecular Genetics Group, Division of Clinical Sciences, John Curtin School of Medical Research, P.O. Box 334, Canberra, A.C.T. 2601, Australia §University Department of Clinical Chemistry, Royal Infirmary, Edinburgh EH3 9YW, U.K. IIIstituto di Scienze Biochimiche, Facolt'a di Medicina, Universita 'G. D'Annunzio', 1-66100 Chieti, Italy ¶Cancer Research Campaign, Molecular Toxicology Group, University College and Middlesex Hospital Medital School, Windeyer Building, Cleveland Street, London WIP 6DB, U.K. **Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY 10461, U.S.A. ttDepartment of Toxicology, The Karolinska Institute, Box 60400, S-104 01 Stockholm, Sweden ttDepartment of Biochemistry, University of Tokyo, Faculty of Medicine, Tokyo 113, Japan §§Department of Biochemistry, University of Virginia, Box 440, Charlottesville, VA 22908, U.S.A. 1 i Merck Frosst Centre for Therapeutic Research, P.O. Box 1005, Pointe Claire-Dorval, Quebec H9R 4P8, Canada ¶¶Second Department of Biochemistry, Hirosaki University School of Medicine, Hirosaki 036, Japan ***Molecular Pharmacology Group, Imperial Cancer Research Fund, Hugh Robson Building, George Square, Edinburgh EH8 9XD, U.K. 1. Shows, T. B., McAlpine, P. J., Boucheix, C., Collins, F. S., Conneally, P. M., Frezal, J., Gershowitz, H., Goodfellow, P. N., Hall, J. G., Issit, P., Jones, C. A., Knowles, B. B., Lewis, M., McKusick, V. A., Meisler, M., Morton, N. E., Rubinstein, P., Schanfield, M. S.,

7.

8. 9. 10. 11.

12. 13. 14. 15. 16. 17.

18. 19.

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Received 18 October 1991

Pyrophosphatase-induced Ca2+ release is unrelated to the spontaneous release from inositol 1,4,5-trisphosphate-sensitive Ca2+ stores Ins(1,4,5)P3-sensitive intracellular Ca2+ stores become more sensitive to Ins(1,4,5)P3 as they load with Ca2+ [1-3]. Such behaviour could be important for generating 'quantal' Ca21 release, Ca2' entry and Ca2+ oscillations [1,4,5]. Once the pools reach a critical Ca2+ content, they become sensitive to the basal level of Ins(1,4,5)P3 and release their Ca2+ to produce a spike [1]. Precipitating anions such as P1 increase the Ca2+-accumulating capacity of the pools and thereby prevent the spike [1]. However, a spontaneous Ca2+ release has been reported in the presence of 5 mM-pyrophosphate (PP1) in bovine chromaffin cells [6]. We now report that such Ca2+ release also occurs in rat hepatocytes, and that this release is unrelated to the spontaneous Ca2+ release from overloaded Ins(1,4,5)P3-sensitive pools that we earlier reported. Fig. 1 (a) illustrates how permeabilized hepatocytes sequestered Ca2+ in the presence of 5 mM-PP,. After the initial phase of Ca2+ sequestration when the medium free [Ca2+] fell to 50 nm, the free [Ca2+] spontaneously rose to a new steady state after a latency. A large Ca2+ spike occurred when additional Ca2+ (40 nmol) and 1992