Disease progression is associated with variation in AAT, and low AAT levels promote atherogenesis.

The expanding molecular database provides unparalleled opportunities for characterizing genes and for studying groups of related genes. We use sequences drawn from the database to construct an evolutionary framework for examining the important glycolytic enzyme phosphoglucomutase (PGM). Phosphoglucomutase plays a pivotal role in the synthesis and utilization of glycogen and is present in all organisms. In humans, there are three well-described isozymes, PGMI, PGM2, and PGM3. PGM1 was cloned 5 years ago; however, repeated attempts using both immunological approaches and molecular probes designed from PGM1 have failed to isolate either PGM2 or PGM3. Using a phylogenetic strategy, we first identified 47 highly divergent prokaryotic and eukaryotic PGM-like sequences from the database. Although overall amino acid identity often fell below 20%, the relative order, position, and sequence of three structural motifs, the active site and the magnesium--and sugar-binding sites, were conserved in all 47 sequences. The phylogenetic history of these sequences was complex and marked by duplications and translocations; two instances of transkingdom horizontal gene transfer were identified. Nonetheless, the sequences fell within six well-defined evolutionary lineages, three of which contained only prokaryotes. Of the two prokaryotic/eukaryotic lineages, one contained bacterial, yeast, slimemold, invertebrate, and vertebrate homologs to human PGM1 and the second contained likely homologs to human PGM2. Indeed, an amino acid sequence, derived from a partial human cDNA, that fell within the second cross-kingdom lineage bears several characteristics expected for PGM2. A third lineage may contain homologs to human PGM3. On a general level, our phylogenetic-based approach shows promise for the further utilization of the extensive molecular database.

A cDNA clone encoding the mRNA for the highly polymorphic human enzyme phosphoglucomutase 1 (PGM1; EC 5.4.2.2) has been isolated and characterized. This was achieved indirectly by first isolating a rabbit cDNA from an expression library using anti-rabbit PGM antibodies. A comparison of the nucleotide sequences shows that the homologies between human and rabbit PGM1 mRNAs are 92% and 97% for the coding nucleotide sequence and the amino acid sequence, respectively. The derived rabbit amino acid sequence is in complete agreement with the published protein sequence for rabbit muscle PGM. A physical localization of the human PGMI gene to chromosome lp3l has been determined by in situ hybridization. Analysis of DNA from a wide variety of vertebrates indicates a high level of PGMI sequence conservation during evolution.Phosphoglucomutase (PGM; EC 5.4.2.2) catalyzes the interconversion of glucose 1-phosphate and glucose 6-phosphate and thus has a pivotal role in glycolysis and gluconeogenesis. The human enzyme is encoded by three autosomal unlinked structural loci, designated PGMJ, PGM2, and PGM3 (1, 2), and there is evidence for a fourth locus expressed in human milk (3). On the basis of protein studies, it is assumed that the loci arose by gene duplication and evolved separately to provide the present day isozymes, showing distinctive properties, such as molecular size (4), thermostability (5), substrate specificity (6), tissue distribution (7), and sulfhydryl group reactivity (8). Multiple isozymes, attributable to multiple PGM loci have been identified in a very wide range of species and it is evident that the initial PGM gene duplication(s) occurred in the remote evolutionary past.Isozyme polymorphism of human PGMI was identified more than 25 years ago (9) and the locus has since been shown to exhibit a very high incidence of both common and rare allelic variation in all populations (10). The PGMI locus is an important anchor point for linkage analysis and for positioning markers on human chromosome lp and its homologues in other species. The heterozygosity demonstrable by isozyme analysis of human erythrocytes [0.81 in the Centre d'Etude Polymorphisme Humain (CEPH) family panel for example] is comparable to several of the variable number tandem repeat loci and exceeds most of the restriction fragment length polymorphisms recognized by other probes on chromosome 1. The PGM1 isozyme polymorphism is a particularly useful marker of individuality in forensic science (11, 12) since the discriminating power of the PGMI locus (1 -probability of a match) is about 0.75 for the common isozyme phenotypes revealed by isoelectric focusing (12). Furthermore, the isozymes are found in a variety of body fluids and enzyme activity is retained for prolonged periods in stains recovered from scenes of crimes.