High-recovery protein purification by high-performance gel-permeation chromatography: application to human serum biotinidase

Size-exclusion chromatography of biological samples which contain extremely alkaline proteins

An improved size-exclusion chromatography (SEC) was developed to isolate extremely basic (alkaline) proteins, such as trypsin (pI=10.5), lysozyme (pI=11), and histone (pI=10.8). Develosil 300 Diol-5 (300 x 8 mm I.D., 30 nm average pore diameter) column was used with an eluent of 0.1 M sodium phosphate, 1.5 M sodium chloride, glycerol (40%, v/v), 2-propanol (10%, v/v), and Brij-58 (1%, v/v). Under these conditions, the final apparent pH becomes to 4.0, and pH adjustment is not necessary. Column temperature and flow rate were 15 degrees C and 0.2 ml/min, respectively. This elution system is stable and reliable, and applications onto human pancreatic juice, human bile, and tissue homogenates were successfully achieved. Since this system is convenient for protein analysis, it is expected to be generally applicable to clinical and biochemical research for identifying protein components in combination with microsequencing.

High-performance liquid chromatographic separation of biotinylamide analogues used as substrates in biotinidase radioassays

A simple, one-step protocol for synthesizing biotinylmono[125I]iodotyramine and biotinyldi[125I]iodotyramine, which are used as tracer substrates in biotinidase radioassays, is presented. This synthetic protocol uses reversed-phase HPLC for the isolation of the biotinylamide analogues from the reaction mixture. The HPLC method developed can potentially be applied to a scaled-up synthetic protocol for non-radioactive biotinylmono- and diiodotyramine. In addition, it can be used for the identification of the above-mentioned compounds.

High-performance gel-permeation chromatographic analysis of protein aggregation. Application to bovine carbonic anhydrase

Protein association in bovine carbonic anhydrase (bCA) was investigated by high-performance gel-permeation chromatography (HPGPC). It was shown that bCA undergoes a time-dependent aggregation after freezing and storing at -20 degrees C. The addition of 50% ethylene glycol or glycerol prevented the aggregation. The HPGPC data were confirmed by the use of cross-linking with subsequent sodium dodecyl sulphate-polyacrylamide gel electrophoretic analysis. The esterase activity of the aggregated bCA was comparable to that of the monomer, suggesting that the observed protein association does not affect the esterase catalytic centre of bCA. This study illustrates how HPGPC can be a convenient and reliable tool for monitoring storage-induced aggregation of proteins.

Improved high-performance liquid chromatographic determination of biotinidase activity with biotinyl-6-aminoquinoline as substrate

An improved high-performance liquid chromatographic assay method for biotinidase activity was developed using the fluorimetric substrate biotinyl-6-aminoquinoline, which was found to be more specific than the biotinyl-4-aminobenzoate previously used. The new method measures the intensity of the fluorescent signal at wavelengths (excitation 350 nm; emission 550 nm) longer than those (excitation 276 nm; emission 340 nm) for 4-aminobenzoate. The analysis of fluorescence in the visible spectrum reduced considerably the number of interfering peaks compared with analysis in the ultraviolet region. This method also made it possible to measure the biotinidase activity directly in samples usually difficult to calculate, such as human and bovine milk or porcine serum; the use of biotinyl-6-aminoquinoline allowed the analysis of the enzyme reaction in milk and porcine serum without pretreatment or dialysis. Stoichiometric increase and decrease of the substrate and product, respectively, were demonstrated. Michaelis constants for biotinyl-6-aminoquinoline were measured at various stages of partial purification. Because the solubility of these synthetic substrates in the aqueous phosphate buffer is limited, the determination of both Michaelis constant and maximum velocity by extrapolation may be helpful for the characterization of the kinetics of biotinidase.