Purified pyruvate kinases type M2 from unfertilized hen's egg are substrates of protein kinase C

Pyruvate Kinase Is Required for Sex Pheromone Biosynthesis in Helicoverpa armigera

Pyruvate kinase (PYK) is a speed-limited enzyme of glycolysis that catalyzes the formation of pyruvate, and plays an important role in acetyl-CoA synthesis. The acetyl-CoA is the precursor of sex pheromone biosynthesis in Helicoverpa armigera. However, the role of PYK in sex pheromone biosynthesis remains elusive. Here, PYK in H. armigera (HaPYK) was found to be highly expressed in the pheromone glands (PGs). The developmental expression profile of HaPYK was consistent with the fluctuation of sex pheromone release. Function analysis revealed that the knockdown of HaPYK led to a decrease in the levels of pyruvic acid and acetyl-CoA in PGs, which in turn caused a significant decrease in cis-11-hexadecenal (Z11-16: Ald) production, female capability to attract males, and mating frequency. Further study demonstrated that sugar feeding (5% sugar) increased the transcription and enzyme activity of HaPYK, thereby facilitating sex pheromone biosynthesis. Moreover, pheromone biosynthesis activating neuropeptide (PBAN) upregulated HaPYK activity through protein kinase C (PKC), as shown by PKC-specific inhibitor analysis. Altogether, our results revealed that PBAN activated HaPYK by Ca²⁺/PKC, thereby regulating the synthesis of pyruvate and subsequent acetyl-CoA, ensuring the supply of sex pheromone precursor, and finally facilitating sex pheromone biosynthesis and mating behavior.

Use of a novel method to find substrates of protein kinase C delta identifies M2 pyruvate kinase

Protein kinase C (PKC) family members have been implicated in numerous cellular processes. However, identifying the substrates of each PKC isozyme remains a challenge. Here, we describe a method using two-dimensional (2D) isoelectric focusing gel electrophoresis to identify substrates of delta PKC (deltaPKC) in MCF-7 breast carcinoma cells. We show that M2 pyruvate kinase is a substrate of deltaPKC, and further characterize the interaction between M2 pyruvate kinase and deltaPKC in MCF-7 cells by immunoprecipitation. deltaPKC activation in vitro or in cells did not appear to alter the enzyme activity or polymerization of M2 pyruvate kinase.

1,25-dihydroxyvitamin D3 inhibits proliferation of IMR-90 human fibroblasts and stimulates pyruvate kinase activity in confluent-phase cells

This study tested the hypothesis that 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) plays a role in regulating some aspects of metabolism in IMR-90 normal human fetal lung fibroblasts. Among the enzymes studied, only pyruvate kinase showed a significant increase after treatment of confluent-phase cells with 1,25(OH)2D3 at various concentrations (0.1-100 nM range) for 24 h. A parallel increase in lactate output was observed. Steroid specificity was established by the failure of 10 nM levels of 25-hydroxyvitamin D3, estradiol-17 beta and progesterone to affect pyruvate kinase activity. The determination of the time course of [3H]-2-deoxy-D-glucose transport indicated that the hormone did not influence the transmembrane transport system of D-glucose. The addition of the inhibitors cycloheximide and actinomycin D to the culture medium abolished, at least in part, the 1,25(OH)2D3 stimulation of pyruvate kinase activity, suggesting the probable dependence of the hormone effect on cellular RNA and protein synthesis. 1,25(OH)2D3 also affected fibroblast growth and DNA synthesis. Cell number significantly decreased after 2-5 days treatment with 10 nM hormone in comparison with control fibroblasts, and also the incorporation of [3H]thymidine into DNA decreased after treatment of the cells with 1 and 10 nM hormone for 48 h. In conclusion, these data demonstrate that 1,25(OH)2D3 stimulates pyruvate kinase activity in confluent-phase IMR-90 human fibroblasts by a mechanism probably dependent on de novo protein synthesis, and also affects cell growth and DNA synthesis in sub-confluent-phase cells.

Antagonizing effects of phorbol 12-myristate 13-acetate on hormonally stimulated gluconeogenesis in isolated rat hepatocytes involve activity changes of pyruvate kinase

The tumor-promoting phorbol ester phorbol 12-myristate 13-acetate partially neutralized the stimulatory effects of epinephrine (alpha 1-adrenergic actions), glucagon, and dibutyryl-cAMP on gluconeogenesis in isolated hepatocytes of fasted rats, when lactate or dihydroxyacetone was used as the substrate. By constructing metabolic crossover plots and by comparing rates of lactate production from dihydroxyacetone with K0.5 values of extracted pyruvate kinase for phosphoenolpyruvate, we obtained evidence that phorbol ester actions on hormonally stimulated gluconeogenesis were accompanied by proportionate increases in activity of pyruvate kinase. Although purified pyruvate kinase from rat liver was a substrate for protein kinase C in vitro, phosphorylation was not accompanied by modulation of kinetic parameters. Furthermore, incubation of pyruvate kinase extracted from hormone-treated hepatocytes with protein kinase C revealed no activation of the prephosphorylated enzyme. This and the absence of effects of the phorbol ester on basal rates of gluconeogenesis and lactate production suggest that effects of protein kinase C on pyruvate kinase activity in hepatocytes may result from impairment of steps at the level of hormone-induced signal transduction.

Phylogeny congruence analysis and isozyme classification: the pyruvate kinase system

As the isozymes of pyruvate kinase (PK) are best known in rats, the characteristics of the rat isozymes are generally used to classify the PK isozymes in other species. Given the discrepancies generated by this classification by analogy, we evaluated a classification using a phylogeny congruence analysis of the compositional relatedness of vertebrate PK's. While our phylogenetic analysis confirmed the well established separation of the L and R isozymes from the K and M isozymes, its power became most evident in the identification of non-orthologous (or variant) forms of PK. Our analysis emphasized the uniqueness of chicken liver PK which cannot be classified either as a K or an L isozyme, confirmed that tumors express a variety of forms of PK, and indicated that lungs systematically express PK's which are not orthologous with PK's from other tissues. The determination of orthology by the phylogeny congruence analysis assumes that the structural data from different sources are subject to similar methodological error. However, we cannot reject the possibility that an apparent lack of orthology be due to artifacts during purification and analysis.

Subunit-specific phosphorylation of pyruvate kinase in medullary thyroid carcinomas of the rat

Pyruvate kinase from anaplastic medullary thyroid carcinomas contains predominantly K-type subunits, whereas pyruvate kinase from differentiated medullary thyroid carcinomas consist of M- and K-type subunits in about equal proportion. In order to analyse the incorporation of phosphate in the respective isozymes after endogenous phosphorylation of cytosolic extracts with [32P]ATP, homotetrameric isozymes as well as heterotetrameric hybrids of differentiated tumors were resolved by affinity chromatography on Blue-Sepharose CL-6B and, if necessary, further purified by immunoprecipitation. SDS-polyacrylamide gel electrophoresis of purified isozymes and subsequent autoradiography showed the incorporation of phosphate in the K4-type isozymes, but not in the other isozymes. The phosphorylation appeared to be cAMP-independent and occurred on a serine residue.

Demonstration of a heterogeneous distribution of glycolytic enzymes and of pyruvate kinase isoenzymes types M1 and M2 in unfertilized hen eggs

The intracellular distribution of the glycolytic enzymes hexokinase, glyceraldehyde-3-phosphate dehydrogenase, lactate dehydrogenase and the pyruvate kinase isoenzymes type M1 and type M2 within unfertilized hen eggs was studied. Most of glycolytic enzyme activities were found in the yolk fraction; 8-24% of total glycolytic enzyme activities were found in the vitelline membrane fraction. However, the specific activities of these enzymes in the vitelline membrane fraction are 19-72-fold higher (U/mg protein) and 45-178-fold more concentrated (U/g wet weight) than in the yolk fraction. The study of intracellular localization of pyruvate kinase isoenzymes shows that the blastodisc, latebra and vitelline membrane contain only pyruvate kinase type M2, whereas pyruvate kinase types M1 and M2 are found in the egg yolk. The exclusive occurrence of pyruvate kinase type M2 in the blastodisc is consistent with the concept that this isoenzyme is involved in the cell proliferation. The heterogeneous distribution of the glycolytic enzymes hexokinase, glyceraldehyde-3-phosphate dehydrogenase and lactate dehydrogenase, and the heterogeneous localization of the pyruvate kinase isoenzymes types M1 and M2 indicate that glycolysis is distributed heterogeneously within the unfertilized hen egg cell.