FUCA

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α-L-Fucosidase (AFU) is a kind of lysosomal acid hydrolase. In 1980, French scholar Deugnier et al. found that AFU has good sensitivity in diagnosing hepatocellular carcinoma, and the positive rate is high. It is the positive rate of AFP. More than three times, it is of great value in the diagnosis of AFP-negative cases and small cell liver cancer, and is a useful indicator for the diagnosis of early primary liver cancer. It has been confirmed by many researches.

Figure 1. Structure of alpha-L-fucosidase.

Biochemical properties

AFU is mainly involved in the catabolism of various fucosyl-containing glycolipids, glycoproteins, mucopolysaccharides and other macromolecular substances. It is widely present in lysosomes and body fluids of various tissues of the human body. Serum, urine, saliva, tears and other specimens are acceptable. The specimens should be clarified and stored at 4°C for 3 days, and at -20°C for 3 months. Avoid repeated freezing and thawing. Hemolysis, jaundice, hyperlipidemia, and contaminated specimens seriously affect the results.

Clinical significance

• Liver cancer

The AFU activity in the serum of patients with primary liver cancer is not only significantly higher than that of normal controls, but also significantly higher than that of metastatic liver cancer, cholangiocytic cells, malignant mesothelioma, malignant hemangioendothelioma, liver cirrhosis, congenital liver cysts and others Benign liver space-occupying lesions. The positive rate for the diagnosis of primary liver cancer is 64%-84%, and the specificity is about 90%. Through the AFU and AFP tests of patients with primary liver cancer and liver cirrhosis, it was found that the AFU and AFP of patients with primary liver cancer and liver cancer after liver cirrhosis increased. With AFP500ng/mL as the critical value for the diagnosis of liver cancer, the false positive rate was 43 %, AFU740nmol/ (ml.h) is the critical value, the sensitivity is 84%, and the specificity is 94%. Therefore, serum AFU has high sensitivity and specificity for the diagnosis of primary liver cancer. A domestic study of 24 cases of hepatocellular carcinoma patients with serum AFU and AFP found that the sensitivity of AFU diagnosis must be 87%, the specificity is 78%, while AFP is 65% and 89% (diagnostic limit is 20ug/L). It is suggested that the sensitivity of AFU diagnosis is better, but the specificity is lower than that of AFP. The activity and positive rate of AFU in serum have no obvious correlation with the diameter of liver cancer. The positive rate of serum AFU in the small liver cancer group was 70.8%, which was significantly higher than that of AFP (37.5%). The positive rate of serum AFU is 80.8% in patients with negative AFP and elevated AFP which is not enough to diagnose primary liver cancer. Liver biopsy is confirmed as primary liver cancer, the positive rate of serum AFU is more than 3 times that of AFP. Detection of AFU in patients with liver cirrhosis, if its activity increases, is more valuable for finding some smaller tumors, at this time AFP cannot make a diagnosis of smaller tumors. Therefore, the application and promotion of AFU as a new diagnostic index for primary liver cancer is of great significance, especially the diagnostic value of AFP negative and small cell liver cancer. Since there is no obvious correlation with AFP, the initial diagnosis can be made, and the combined detection can increase the detection rate of liver cancer.

• Pregnancy and ovarian tumors

Studies have shown that plasma AFU increases as the number of weeks of gestation increases, and after natural delivery or artificial termination of pregnancy, it drops rapidly and returns to normal within 5 days. The activity of serum AFU in patients with ovarian cancer decreases, and it has nothing to do with disease stage, tumor burden, histological type and tumor differentiation. Decreased serum AFU activity in patients with benign and malignant ovarian cancer may be related to genetic factors.

• Others

In patients with fucosidase storage, due to lack of AFU or decreased activity in congenital tissues, organs and body fluids, glycoprotein or glycolipid metabolism disorder occurs. Serum AFU is elevated in patients with gastric cancer, but not in acute pancreatitis, but it is decreased when cystic fibrosis is accompanied by pancreatitis, and serum AFU activity is decreased in progressive pyramidal dystrophy.