An electrophoretic investigation of the cytosolic di- and tripeptidases of fish: molecular weights, substrate specificities, and tissue and phylogenetic distributions

Genetic subdivision, glacial refugia and postglacial recolonization in the golden-striped salamander, Chioglossa lusitanica (Amphibia: urodela)

The golden-striped salamander (Chioglossa lusitanica) is an ecologically specialized species, endemic to north-western Iberia. Patterns of genetic variation were assessed at seven polymorphic enzyme loci and one mitochondrial DNA (mtDNA) marker (cytochrome b) in 17 populations across its range. Estimates of enzyme genetic diversity revealed a high degree of genetic subdivision (FST = 0.68), mainly attributable to the existence of two groups of populations. The groups were located, respectively, north and south of the Mondego River, indicating that this river coincided with a major historical barrier to gene flow. A significant decrease in genetic variability from the Mondego northwards was associated with the Douro and Minho rivers. mtDNA sequence variation revealed a congruent pattern of two haplotype groups (d = 2.2%), with a geographical distribution resembling that of allozymes. The pattern and depth of genetic variation is consistent with the following hypotheses: (i) subdivision of an ancestral range of the species prior to the middle Pleistocene; (ii) secondary contact between populations representing historical refugia; (iii) relatively recent range expansion giving rise to the northern part of the species range; and (iv) loss of genetic variation through founder effects during range expansion across major rivers.

Assignment of six enzyme loci to multipoint linkage groups in fishes of the genus Poeciliopsis (Poeciliidae): designation of linkage groups III-V

Three new linkage groups of enzyme loci are described using Poeciliopsis monacha x P. viriosa-derived interspecific backcross hybrids. Comparison to known linkage groups of the confamilial genus Xiphophorus shows homology between Xiphophorus linkage group I and Poeciliopsis linkage group III, Xiphophorus linkage group II and Poeciliopsis linkage group I, and Xiphophorus linkage group IV and Poeciliopsis linkage group IV. Comparison of the gene content of other fish, amphibians, and mammal syntenic groups suggests retention of plesiomorphic vertebrate gene arrangements in at least two poeciliid linkage groups. Expansion of the Poeciliopsis gene map should be of utility in the identification of tumor regulatory genes through demonstration of linkage to biochemical markers.

Avian peptidase isozymes: tissue distributions, substrate affinities, and assignment of homology

Peptidase (EC 3.4.13.9 and EC 3.4.13.11) isozymes were examined from 14 tissues of 19 species of birds, representing 8 families and 6 orders, via horizontal starch gel electrophoresis. Peptidases were detected by employing histochemical staining techniques utilizing 13 di-, tri-, and tetrapeptides as substrates. It was determined that there is a minimum of six presumptive structural gene loci encoding peptidases in birds (excluding those encoding cytosol aminopeptidase; EC 3.4.11.1). The products of the peptidase loci were widely expressed in most tissues with the exception of Pep-F, which was restricted to pancreas. Products of most loci have multiple, overlapping substrate affinities (except for the products of Pep-D, which react only with a peptide containing a carboxyterminal proline). By using a combination of differential electrophoretic mobility and substrate preferences, the products of the various peptidase loci can be distinguished from one another. The homologies of the avian peptidases with those in other vertebrates were tentatively established and it is suggested that the nomenclature proposed by Rapley et al.

Peptidases A, B, C, D and S in the American mink: polymorphism and chromosome localization

An electrophoretic analysis of peptidases was carried out in a population of American mink. Based on substrate and tissue specificities, as well as subunit composition, homologies were established between mink peptidases A, B, C, D and S and human peptidases. Polymorphism for peptidases B and D was demonstrated for minks of three coat colour types. Breeding data indicated that the peptidase variations are under the control of allele pairs at distinct autosomal loci designated as PEPB and PEPD, respectively. Using a panel of American mink-Chinese hamster hybrid clones, the gene for PEPB was assigned to mink chromosome 9.

Genetic structure of natural populations of the red-spotted newt, Notophthalmus viridescens

Genetic variation is described at 15 loci in 2 neotenic and 12 nonneotenic populations of red-spotted newts. Though high levels of genetic similarity (I = 0.990) were found among all populations, allele frequencies at six of the eight most polymorphic loci show significant heterogeneity across populations. Change in allele frequencies at two of these loci (Pep-2 and Ldh-1) is significantly correlated with latitude. Interspecific homologies are established for newt peptidases based on substrate specificities and lactate dehydrogenases based on tissue distribution, thermal stability, and kinetic properties. Nonneotenic populations are highly variable (H = 0.157) and neotenic populations are only slightly, but significantly, less variable (H = 0.120). The high levels of heterozygosity detected in nonneotenic populations may result from large effective population size and/or environmental heterogeneity. The unexpectedly high heterozygosity values obtained for the neotenic populations may indicate adult dispersal or the presence of some previously undetected red efts at these localities. In any case, a major change in life history has apparently had little effect on the genetic structure of these populations.

An electrophoretic and immunological reinvestigation of the cytosolic di- and tripeptidases of the guinea pig

Electrophoretic and immunological techniques have been used to analyze the cytosolic di- and tripeptidases of guinea pigs. In contrast to previous reports utilizing intestinal mucosa extracts, cavian peptidases were found to be similar to peptidases described in other mammals and in fishes. Earlier papers are in error owing to coelectrophoresis of enzymes and to impure enzyme preparations. Guinea pigs are unusual in that they appear to lack peptidase C.