Happily at Work

Abstract

It is a great privilege to be asked for a "Reflections" essay; I admire those prepared by my predecessors. My teachers were less prestigious than Arthur Kornberg's (1), and there was no single major theme in my research as was the case with several previous contributors to this series. Instead we studied a wide variety of metabolic phenomena that I have described in a summary of my first 50 years of biochemical research (2).Our findings included a treatment for selenium poisoning in livestock (undergraduate thesis; selenium-containing mercapturic acids are excreted in the urine) that was applied successfully to a human case; our studies of spermatozoa will be described in a following section. We elucidated the mechanism by which L-glyceraldehyde inhibits glycolysis (3). That disproved Needham's non-phosphorylating glycolysis in embryos and tumors. Could that have encouraged him to drop experiments and to devote his talents to prepare his magnificent history of Chinese science instead? We found that the function of biotin was to fix CO 2 in heterotrophic organisms (4); cellular respiration rates varied with the availability of inorganic P and phosphate acceptor (5, 6); propionate was metabolized by CO 2 addition to ultimately yield succinate (7,8). My students purified and crystallized some 10 phosphate-transferring enzymes, and we demonstrated that most of them required MgATP as substrate and were inhibited by free ATP; we found 16 different antibiotics that affected oxidative phosphorylation (9, 10) and a dozen that acted as ionophores (11), some of which are still being used in experiments. We also found that caffeine increased respiration and dramatically induced whiplash-type motility in sperm by increasing cyclic AMP (12, 13); the respiratory response was dependent on the utilization of acetylcarnitine (14). Thyroid hormone and also dehydroepiandrosterone induced the synthesis of mitochondrial glycerol-3-phosphate dehydrogenase to as much as 20 times the normal concentration (15-17) and formed part of a thermogenic system (17, 18). The path of carbon in gluconeogenesis was found to involve carboxylation of pyruvate (Utter reaction) in mitochondria, reduction of oxalacetate to malate, malate transport to cytosol in exchange for pyruvate, oxidation of malate to oxalacetate (the precursor of phosphopyruvate) together with the generation of the NADH required to reduce 3-phosphoglycerate to triose phosphate (19,20); serine was found to be converted to glucose by an entirely different pathway, probably the reverse of its synthesis from hydroxypyruvate (21). We also found that levels of liver cytosolic phosphoenolpyruvate carboxykinase (PEPCK) are regulated by the need for gluconeogenesis; they are increased by fasting and decreased in well fed animals; PEPCK is activated by ferrous ion, and in liver free calcium activates PEPCK by releasing Fe 2ϩ from mitochondria to the cytosol (22); feeding tryptophan inhibits gluconeogenesis because its metabolite, quinolinate, forms a complex with ferrous ion that blocks PEPC...

Co-evolution of steroidogenic and steroid-inactivating enzymes and adrenal and sex steroid receptors

“…DHEA, pregnenolone and 5-Adiol are readily hydroxylated at C7 (Akwa et al, 1992;Lathe, 2002;Lardy, 2003). Moreover, these 7 -11 hydroxy-and 7 -hydroxy-steroids can be oxidized to 7-oxo-steroids [ Figure 4].…”

Thermodynamics of the Pyruvate Kinase Reaction and the Reversal of Glycolysis in Heart and Skeletal Muscle

“…Despite early statements of Meyerhof et al (3) that the reaction was irreversible, Lardy and Ziegler (4) experimentally showed in rat muscle extracts its reversibility in 1945 from the exchange of 32 P between P-enolpyruvate and ATP. These workers further showed that P-enolpyruvate could be synthesized directly from pyruvate in a system where ATP was constantly being regenerated and that the rate of reaction increased with increasing potassium concentration (4,5). The reversibility of the reaction in muscle extracts was subsequently shown by Krimsky (6) and McQuate and Utter (7) in 1959 and again by Dyson et al (8) in 1975.…”

SPINK3 modulates mouse sperm physiology through the reduction of nitric oxide level independently of its trypsin inhibitory activity

“…However, the physiological role, the mechanism by which they prevent intracellular Ca 2C increase and the signaling pathways that they modulate are still unknown. In addition, although some of them have trypsin inhibitor activity (Lardy 2003), whether their caltrin function is related to its trypsin inhibitory activity remains to be demonstrated. Therefore, our first aim was to study the possible interaction between SPINK3 Ca 2C uptake inhibition and the levels of NO in mouse sperm during capacitation.…”