Ostrich intestinal glycohydrolases: distribution, purification and partial characterisation

Area of Science:

• Biochemistry
• Enzymology
• Avian Physiology

Background:

• Intestinal glycohydrolases are crucial for carbohydrate assimilation.
• Avian maltase-glucoamylase (MG) complexes are poorly understood.
• This research focuses on characterizing ostrich intestinal enzymes.

Purpose of the Study:

• To characterize avian intestinal maltase-glucoamylase (MG) and sucrase-isomaltase (SI) from ostriches.
• To perform the first kinetic analysis of an avian MG.
• To determine the subunit composition and kinetic parameters of ostrich intestinal glycohydrolases.

Main Methods:

• Purification of MG and SI from ostrich intestinal brush border membrane vesicles using various chromatography techniques (Sephadex G-200, Tris-affinity, Toyopearl-Q650, phenyl-Sepharose).
• Analysis of enzyme subunits via SDS-PAGE.
• Kinetic studies of hydrolysis for linear oligosaccharides, starch, and glycogen.

Main Results:

• Ostrich MG and SI exhibit highest activity in the jejunum.
• Ileal MG consists of three subunits (M(r) 145,000, 125,000, and 115,000), with the 115,000 subunit homologous to porcine MG.
• Optimal activity observed at pH 6.5 (for maltose, starch, isomaltose) and 5.5 (for sucrose), with peak activity at 58°C; longer maltooligosaccharides are hydrolyzed less efficiently.

Conclusions:

• Ostrich MG and SI share significant similarities in physicochemical properties, suggesting potential complex formation.
• The study provides novel insights into the kinetics and structure of avian MG.
• Findings contribute to understanding carbohydrate digestion mechanisms in birds.