Ribonucleases of chronic granulocytic leukaemia leucocytes

The isolation, purification, and properties of a ribonuclease (Mr 18 000) from human uremic serum, and its relation to the human urinary ribonuclease (Mr 33 000). II. Properties of the enzymes

A low molecular weight ribonuclease (Mr 18 000) isolated and purified from human uremic serum was found to have similar properties to the high molecular weight ribonuclease (Mr 33 000) isolated from human urine. A detailed comparative study of both enzymes was undertaken to investigate the relationship between them. It is suggested that poly(C)-avid human ribonucleases have similar amino acid compositions but variable carbohydrate contents and that variations in the sugar content are responsible for variations in the molecular weight.

Alteration of human serum ribonuclease activity in malignancy

A review of the literature and current biochemical studies is presented which provides significant evidence of alteration in the level of the enzyme ribonuclease activity in cancer. Current studies reveal that 80% of all cancer patients have alteration in ribonuclease activity and that individuals known to be at high risk for the development of cancer also demonstrate significant alteration of ribonuclease activity. It is noted that while elevation of serum ribonuclease exists within the cancer state and appears to be independent of clinical status (relapse, remission, or cured), diminished activity is found within the tumor itself. Animal models are reviewed which demonstrate that ribonuclease activity becomes elevated in the murine species subsequent to the transplantation of tumor and following the infection of the host with oncogenic virus. The occurrence of elevated ribonuclease activity in high tumor incidence strain mice long before the development of overt tumor is alos discussed. To date it is not possible to assign a specific function to the changes in the level of ribonuclease in connection with the cancer state. However, evidence indicating that tumor chemotherapy is generally associated with early elevation of ribonuclease activity within the tumor cell suggests that increased ribonuclease activity may play a role in the process by which the host restricts neoplastic transformation. The potential of this enzyme as a biochemical marker in cancer is discussed.

Ribonuclease activity in plasma and leucocytes of malnourished children

RNAase activity was measured in plasma and leucocytes of manourished children. In subjects suffering from kwashiorkor, alk. RNAase levels in plasma and leucocytes were markedly raised and they returned to normal after therapy. However, the enzyme activity was not altered in undernourished children. These data indicate that circulating level of alkaline. RNAase is not a useful parameter for detecting milder grades of protein-calorie malnutrition (PCM).

Purification and properties of alkaline ribonuclease from human serum

1. Five alkaline ribonucleases (EC 3.1.4.22) were purified about 140- to 1900-fold from human serum by phosphocellulose and DEAE-cellulose chromatographies and Sephadex G-75 filtration, with a total recovery of 22%. These were designated as RNAases 1-5. 2. Optimum activities were observed at pH 8.5-8.7 for RNAases 1-4, and at pH 7.5 for RNAase 5. The molecular weights of these enzymes were estimated by gel filtration as 45 000, 32 000, 20 000, 13 000 and 8500, respectively. 3. These RNAases were found to be heat-labile proteins but are markedly stabilized with bovine plasma albumin. The reaction was activated by Na+, K+, Mg2+ and Ca2+, and inhibited by Co2+, Fe2+, Cu2+ and Zn2+. EDTA had little effect on the velocity of the reaction. Spermine caused 2- to 7-fold activation. 4. Among the substrates examined, these RNAases preferentially hydrolyzed pyrimidine bodies and except for RNAase 5 had a higher affinity for poly(C) than poly(U) as substrate. Each enzyme was free from other nucleolytic enzymes and hydrolyzed only RNA.