Molecular size of hagfish muscle lactate dehydrogenase.

In contrast to an earlier report, we find that the primitive vertebrate Eptatretus possesses a muscle lactate dehydrogenase whose molecular size is like that of lactate dehydrogenases from higher vertebrates. The molecular size of lactate dehydrogenase appears to have remained constant during evolution.

Immunological detection of single amino acid substitutions in alkaline phosphatase.

Antiserums to wild-type alkaline phosphatase from Escherichia coli were prepared and tested for reactivity with phosphatases altered by point mutations. Eight out of the nine mutant enzymes were distinguished from the wild type with quantitative microcomplement fixation. The structural changes are among the smallest yet observed immunologically.

Enzyme evolution in the Enterobacteriaceae.

An immunological approach has been used for the study of alkaline phosphatase evolution in bacteria of the family Enterobacteriaceae. Antisera were prepared against alkaline phosphatase from Escherichia coli and Klebsiella aerogenes and tested against the unpurified alkaline phosphatases of 32 strains of enterobacteria by double diffusion and quantitative micro-complement fixation. The immunological relationships detected among the alkaline phosphatases of enterobacteria agree approximately with those reported for five other enzymes, as well as with the tryptic peptide pattern similarities found for two other enzymes, and with the relationships detected by interspecific deoxyribonucleic acid hybridization tests.

Evolution of L-1, 2-propanediol catabolism in Escherichia coli by recruitment of enzymes for L-fucose and L-lactate metabolism.

A mutant strain of Escherichia coli capable of growth on l-1,2-propanediol was isolated previously. The mutant is characterized by constitutive production of a propanediol:nicotinamide adenenine dinucleotide (NAD) oxidoreductase which is essential for the new growth property. In the present study, it is shown that phage P1 cotransduces the genetic locus conferring this property and the genes for the utilization of l-fucose. A further indication of a relationship between these two growth properties is provided by the observation that wild-type E. coli excretes propanediol during fermentation of l-fucose. Under these conditions, a propanediol dehydrogenase (lactaldehyde reductase) is induced. This enzyme migrates on diethylaminoethyl-cellulose with the propanediol dehydrogenase produced constitutively by the mutant strain. A key event in the establishment of the ability to grow on propanediol is evidently a shift in the expression and function of propanediol dehydrogenase; an enzyme catalyzing formation of a reduced fermentation product anaerobically in wild-type cells functions aerobically to oxidize this same product in the mutant. l-Lactaldehyde, which is thus derived from propanediol, is converted to l-lactate by another dehydrogenase (l-lactaldehyde:NAD oxidoreductase) which is constitutively produced by both wild-type and mutant cells. The normal function of this enzyme is not yet established. l-Lactate is converted to pyruvate by an inducible NAD-independent l-lactate dehydrogenase. Thus, the carbons of propanediol are brought into the central metabolic network of the cell.

Micro-complement fixation in Klebsiella classification.

The alkaline phosphatases of 29 strains of bacteria assigned by various authors to the genera Aerobacter, Klebsiella and Enterobacter were compared by the micro-complement fixation technique. On the basis of phosphatase resemblance, we recommend that all strains hitherto assigned to Aerobacter aerogenes and Enterobacter aerogenes be assigned to the genus Klebsiella.