Herman Kalckar

Herman Moritz Kalckar (1908 -1991) was a Danish biochemist who pioneered the study of cellular respiration. He trained as a medical doctor at the University of Copenhagen but later moved to America, becoming a professor of biology at Johns Hopkins University.

In his work in Denmark, Kalckar showed that phosphate compounds could provide energy, by demonstrating that in frog muscles where glycolysis had been inhibited with iodoacetate, muscular contraction continued for a short period using phosphocreatine as a source of energy. This suggested for the first time that phosphate compounds acted as a link between catabolism and anabolism. These studies were done in close collaboration with Fritz Albert Lipmann.

In America, Kalckar worked with Sidney Colowick and discovered adenylate kinase in 1942, purifying this enzyme from muscle extracts. Further work on nucleotide metabolism allowed him to identify nucleoside phosphorylase, a key enzyme in nucleotide salvage pathways.

Moving on from nucleotides, Kalckar switched his attention to the enzymes involved in galactose metabolism. Here, he characterised galactose-1-phosphate uridylyltransferase and identified the cause of the human metabolic disease galactosemia as a defect in this enzyme.