Structure of human pancreatic lipase

Article Abstract:

The enzyme, triacylglycerol acyl hydrolase, is commonly known as pancreatic lipase. It is involved in the digestion or breakdown of fats from food. The three-dimensional structure of the human enzyme has been determined by X-ray crystallography, in which crystals of the molecules are examined by a X-ray technique known as multiple isomorphous replacement. The primary sequence of the protein has been established by cloning the gene which codes for the enzyme. It is known that if the amino acid, serine, which is in position 152 out of the 449 amino acids, is chemically modified, enzymatic activity is lost. Structural results also show that the serine amino acid residue and two other amino acids, histidine and aspartic acid, comprise the site of enzyme activity. A chemically similar site is necessary for activity of another group of enzymes, the serine proteases, which cleave protein molecules. However, the structure of the site of the pancreatic lipase differs from the serine proteases. The pancreatic enzyme molecule is structurally divided into two folding units. A loop structure covers the site of enzyme activity. The shape of the molecule probably changes when it is in contact with the fatty acids that it digests. (Consumer Summary produced by Reliance Medical Information, Inc.)

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... And turn back again

Article Abstract:

The evolutionary relationship of turtles to other reptiles is a contentious issue amongst scientists. Traditional theory places turtles basal to other reptiles due to the absence of temporal fenestrae. O. Rieppel and M. deBraga analysed morphological characters and concluded that turtles could be placed in the crown group Diapsida. Other scientists dispute this placement, but phylogenetic analysis of the amino-acid sequence of pancreatic polypeptide of turtles and 14 other tetrapod taxa, according to the branch and bound method, supports the view that turtles are diapsids.

Phylogeny, Turtles

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Structure of the pancreatic lipase-procolipase complex

Article Abstract:

Procolipase, the source molecule of the protein cofactor colipase, is made up of three cylindrical regions joined together by disulphide bridges. This structure has a topographic resemblance to snake toxins. Procolipase is important because, by giving rise to colipase, it allows the pancreatic enzyme lipase to bind to the lipid interface. Proclipase binds to the C-terminal domain of lipase without causing conformational alteration.

Enzymes, Pancreas

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