Structural Biochemistry/Shigeru Tsuiki

Introduction
Shigeru Tsuiki was one of the pioneers in the research fields of complex carbohydrates and protein phosphatases. In 1951, after graduated from the Tohoku University Medical School of Japan, he began his career as a biochemist by working in the laboratory. Five years later, he had a chance to visit Dr Ward Pigman- a professor at the University of Alabama Birmingham Medical School after getting his PhD degree, and his contribution began from here. During his prominent career, he accomplished three different outstanding contributions to the biochemistry research field: with the method of purifying mucin from bovine submaxillary glands, identification of four different molecular species of mammalian sialidase, and an establishment of molecular basis for mammalian protein phosphatases.

Mucin Purification
During his visit to one of the leading society of American chemist, he developed an impressive method of mucin purification from using cetyltrimethylammonium bromide. This development greatly contributed to the characterization of peptides structures of mucin. After researching deeply and thoroughly into sialic acid components of mucin, this led him to study the enzyme which involved in sialic acid. He began to focus on the two key enzymes: glutamine-fructose-6 phosphate amidotransferase, and UDP-N-acetylglucosamine (UDP-GlcNAc) 2-epimerase UDP-GlcNAc and CMP-N-acetylneuraminic acid. After seeing different behaviours of these two enzymes during rat liver development, he found out that UDP-GlcNAc 2-epimerase could be obtained from rat liver.

Identification of four different molecular species of mammalian sialidase
At that time, most scientists knew that the removal of sialic acid residue from glycoprotein and glycolipids was the first step in the catabolism of glycoconjugates. With his passion for biochemistry, he continued to develop the four types of sialidase with differences in enzymatic properties and intracellular localization: intralysosomal, cytosolic and membrane-associated sialidases I and II. He experimented this development on rat, and his result showed that some of the tissues in rat contained all these four types.
 * Intralysosomal sialidase- contains narrow substrate specificity.
 * Cytosolic sialidase- hydrolyse glycoproteins and gangliosides.
 * Membrane-associated sialidase I: not often hydrolyse with other substrates.
 * Membrane-associated sialidase II: actively hydrolyse on glycoproteins and gangliosides as cytosolic sialidase.

Establishment of molecular basis for mammalian protein phosphatases
His last major contribution was the study of protein phosphatases. With the interest in biochemical research, he showed that the cellular glycogen content was controlled by itself, and this led him to protein phosphatases. Scientists have found out that the enzyme that was responsible for glycogen synthesis was glycogen synthase (GS), and for glycogen degradation was glycogen phosphorylase (GP). Both enzymes functioned differently: GP catalyses the phosphorolysis of glycogen, and GS catalyses the transfer of glucose from UDP to primer. Based on this information, Dr. Tsuiki investigated the enzymatic properties of the rat liver GS phosphatase. He came up with a way to solubilize rat liver GS phosphatase from glycogen using column chromatography. This method let us know the activity of GS phosphatases by increasing the GS in the absence of glucose-6-phosphate. With the success of carrying out this experiment, Dr Tsuiki began to work on his GS phosphatase project. His strategy was to use column chromatography instead of rat liver extract in order to purify protein phosphatases. The chromatography on DE52 column revealed one major difference in elution profile between GS and GP phosphatases activities. They showed three different peaks IA, IA, and II represented for three distinct proteins.