What is acetylglucosaminidase

Acetyl glucosaminidase is a sensitive marker for detecting renal damage and renal tubules. It can also be used to check for urinary tract infections and early diagnosis of diabetic nephropathy. Its clinical significance usually appears in pathological conditions. If other tests are normal and the acetyl glucosidase level is high, a low-salt, low-fat, high-vitamin diet and quitting smoking and drinking are recommended. Next, let’s take a closer look at the role of acetyl glucosamidase, what we should pay attention to, and how to check it.

Normal values ​​of β-N-acetylglucosaminidase test

1. p-Nitrophenol colorimetric method: serum NAG 21.54±6.4U/L, urine NAG showed normal distribution, the median was 9.13U/g creatinine, and the upper limit of the 95th percentile was 16.10U/g creatinine.

2. Fluorescence spectrophotometry:

Adult serum: 9.94±2.07U/L.

Adult urine: 6.39±3.19U/LCre.

The role of β-N-acetylglucosaminidase test

Blood and urine NAG activity measurements are more sensitive to renal parenchymal lesions, especially acute injuries and active lesions, and are mainly used for monitoring early renal damage and disease observation.

1. Renal tubular disease Heavy metals (mercury, lead, cadmium, etc.) and drug-induced renal damage, ischemia, hypoxia, blood loss, shock, etc. can all cause increased NAG activity.

2. In patients with nephrotic syndrome, urinary NAG often increases significantly, decreases during remission, and rises rapidly during relapse, so it can be used as an indication for clinical observation. The changes in the acute phase of glomerulonephritis are large, but compared with tubular injury, the changes are smaller.

3. Localization diagnosis of urinary tract infection: Elevated urine NAG in acute and chronic pyelonephritis can distinguish it from simple cystitis. It can be used for the diagnosis of early upper urinary tract infection.

4. Monitoring of renal transplant rejection: NAG can be elevated in the early stages of renal transplant rejection and is more sensitive than urine protein, serum creatinine, and creatinine clearance.

5. Early diagnosis of diabetic nephropathy: Elevated urine NAG in diabetic nephropathy is better than urine albumin and β2-microglobulin for early diagnosis of the disease.

Possible diseases with high β-N-acetylglucosaminidase results: nephrotic syndrome, urinary tract infection

What should be paid attention to in the β-N-acetylglucosaminidase test

(1) p-Nitrophenol colorimetric method:

① The matrix p-nitrophenol should be purified and dried at 50℃ for 24h before preparation. Use 10mmol/L NaOH to make the concentration of 0.04mmol/L, and scan the absorption curve with a narrow bandwidth spectrophotometer, λmax=401nm, according to IFCC standards, Aλmax=0.7316～0.7388, Eλmax=18380±90(25℃).

② The substrate has low solubility. When preparing, it should first be adjusted into a paste with an appropriate amount of pH 4.6 buffer, and then the buffer should be gradually added to the required amount.

③ When the measurement result exceeds the linear range, the sample should be diluted with physiological saline and re-measured, and the result should be multiplied by the dilution factor.

④ The concentration of urea enzyme is greatly affected by urine volume, so the 24-hour urine volume should be collected. If the enzyme excretion rate is calculated using the NAG/g creatinine ratio, it will not be affected by urine concentration or dilution, and there is no need to retain urine for 24 hours.

(2) Fluorescence spectrophotometry:

① There is a domestically produced test kit for measuring NAG by fluorescence method, which is highly sensitive and not affected by urine color.

②You can also use the 930 fluorescence photometer produced by Shanghai Third Analytical Instrument Factory, with an excitation filter of 360 and an emission filter of (400+450) composite, with satisfactory results.

③ The concentration of each component in the enzyme reaction solution of this method is: substrate 1.33mmol/L, citric acid 20mmol/L, Na2HPO4 32mmol/L.

④ The solvent used for preparing reagents should be double distilled water, the substrate should contain no free 4-MU, and the enzyme should be absent in BSA or inactivated by heating at 50°C for 2 hours.

⑤ NAG in serum is stable at 4°C for several hours to several days and at -20°C for several months. Urine specimens are stable at 4°C for 1 week and can also be treated with citrate anticoagulated plasma.

⑥ β-N-acetylglucosamine can be hydrolyzed by two enzymes, one is β-N-acetylglucosamine sidase (EC 3.2.1.30) and the other is β-N-acetylglucosidase (EC 3.2.1.52). Only the purified enzyme can be limited to EC 3.2.1.30 or EC 3.2.1.52. Strictly speaking, NAG, which is often referred to in domestic literature, is named after the substrate used, rather than referring to the specificity of the enzyme for the substrate. Therefore, foreign literature currently often refers to it as β-N-acetylglucosaminidase.

Methods for β-N-acetylglucosaminidase testing

(1) p-Nitrophenol colorimetric method: Mix the mixture at a wavelength of 405 nm, a light path of 1 cm, and adjust the light to zero with distilled water. Read the absorbance of each tube and use the difference (AU - AC) to check the standard curve.

① The matrix p-nitrophenol should be purified and dried at 50℃ for 24h before preparation. Use 10mmol/L NaOH to make the concentration of 0.04mmol/L, and scan the absorption curve with a narrow bandwidth spectrophotometer, λmax=401nm, according to IFCC standards, Aλmax=0.7316～0.7388, Eλmax=18380±90(25℃). According to the molar absorption coefficient of p-nitrophenol

② The substrate has low solubility. When preparing, it should first be adjusted into a paste with an appropriate amount of pH 4.6 buffer, and then the buffer should be gradually added to the required amount.

③ When the measurement result exceeds the linear range, the sample should be diluted with physiological saline and re-measured, and the result should be multiplied by the dilution factor.

④ The concentration of urea enzyme is greatly affected by urine volume, so the 24-hour urine volume should be collected. If the enzyme excretion rate is calculated using the NAG/g creatinine ratio, it will not be affected by urine concentration or dilution, and there is no need to retain urine for 24 hours.

(2) Fluorescence spectrophotometry: First, dilute the serum or urine 20 times with a buffer solution that does not contain bovine serum albumin (BSA).

Mix well, set the excitation wavelength to 364nm, the emission wavelength to 448nm, adjust to zero with the stop solution, adjust the fluorescence intensity of the 6μmol/L 4-MU tube to 100, and then measure the fluorescence intensity of the blank tube and the measurement tube respectively.

① There is a domestically produced test kit for measuring NAG by fluorescence method, which is highly sensitive and not affected by urine color.

②You can also use the 930 fluorescence photometer produced by Shanghai Third Analytical Instrument Factory, with an excitation filter of 360 and an emission filter of (400+450) composite, with satisfactory results.

③ The concentration of each component in the enzyme reaction solution of this method is: substrate 1.33mmol/L, citric acid 20mmol/L, Na2HPO4 32mmol/L.

④ The solvent used for preparing reagents should be double distilled water, the substrate should contain no free 4-MU, and the enzyme should be absent in BSA or inactivated by heating at 50°C for 2 hours.

⑤ NAG in serum is stable at 4°C for several hours to several days and at -20°C for several months. Urine specimens are stable at 4°C for 1 week and can also be treated with citrate anticoagulated plasma.

⑥ β-N-acetylglucosamine can be hydrolyzed by two enzymes, one is β-N-acetylglucosamine sidase (EC 3.2.1.30) and the other is β-N-acetylglucosidase (EC 3.2.1.52). Only the purified enzyme can be limited to EC 3.2.1.30 or EC 3.2.1.52. Strictly speaking, NAG, which is often referred to in domestic literature, is named after the substrate used, rather than referring to the specificity of the enzyme for the substrate. Therefore, foreign literature currently often refers to it as β-N-acetylglucosaminidase.

How much does β-N-acetylglucosaminidase test cost?

Specialty Category: Urology Examination Category: Biochemical Examination

Applicable gender: Suitable for both men and women Whether fasting: Fasting

β-N-acetylglucosaminidase test reference price: 10-60 yuan