Isolation, crystallization, and properties of indolyl-3-alkane alpha-hydroxylase. A novel tryptophan-metabolizing enzyme

Tryptophan Side-Chain Oxidase Enzyme Suppresses Hepatocellular Carcinoma Growth through Degradation of Tryptophan

Tryptophan metabolism plays a role in the occurrence and development of hepatocellular carcinoma cells. By degrading certain amino acids, tumor growth can be limited while maintaining the body’s normal nutritional requirements. Tryptophan side-chain oxidase (TSO) enzyme can degrade tryptophan, and its inhibitory effect on hepatocellular carcinoma cells is worthy of further study. To investigate the degradation effect on tryptophan, TSO was isolated and purified from qq Pseudomonas. The reaction products were identified with high performance liquid chromatography (HPLC) and high-performance liquid chromatography tandem mass spectrometry (HPLC-MS). De novo sequencing provided the complete amino acid sequence of TSO. The results of CCK-8, colony formation, transwell, and qPCR confirmed that TSO had inhibitory effects on the proliferation and migration of HCCLM3 (human hepatocarcinoma cell line) and HepG2 cells. The results of flow cytometry confirmed its apoptotic activity. In animal experiments, we found that the tumor-suppressive effect was better in the oncotherapy group than the intraperitoneal injection group. The results of immunohistochemistry also suggested that TSO could inhibit proliferation and promote apoptosis. In conclusion, a specific enzyme that can degrade tryptophan and inhibit the growth of hepatoma cells was authenticated, and its basic information was obtained by extraction/purification and amino acid sequencing.

The Synthesis of L-tryptophan Degrading Bioreactors

To design a bioreactor for removing the potential cancer nutrient L-tryptophan from blood, the L-tryptophan degrading enzyme tryptophan side chain oxydase (TSO) was chemically bound to glutaraldehyde activated gamma amino silane silica and to Zetaffinity microcolumns consisting of a glutaraldehyde activated polyacrylic-cellulose copolymer. Five experiments were carried out in sheep and six experiments in rabbits using a closed circuit plasmapheresis bioreactor system. L-tryptophan in sheep was degraded by the silica bioreactor in a single pass to undetectable levels as measured by high performance liquid chromatography (HPLC). Zetaffinity bioreactors degraded L-tryptophan in rabbits to more than 95% in a single pass. Whole blood L-tryptophan levels changed little throughout the experiment indicating a vast extravascular tryptophan pool. Enzyme leakage from the bioreactor was less than 10−5 IU TSO per ml plasma. The procedures were tolerated well by the animals without any change in vital signs

Depletion of patients' plasma tryptophan using tryptophan side-chain oxidase columns

The use of the enzyme tryptophan side-chain oxidase, isolated from Pseudomonas XA, was explored in 3 patients with refractory acute lymphocytic leukemia. Patients were given either a low-tryptophan diet or tryptophan-free hyperalimentation, prior to and during therapy. Their plasma, separated by pheresis, was continuously passed through a tryptophan depletion column containing the immobilized tryptophan side-chain oxidase. Up to 4 plasma volumes were passed through the column daily, 5 days per week for 2-3 weeks, and plasma tryptophan levels, both free and total, were measured by high-performance liquid chromatography. Pre- and postcolumn plasma samples were collected throughout the pheresis procedure. All postcolumn plasma samples had unmeasurable tryptophan levels throughout the treatment period, whereas precolumn samples were always measurable. Generally, tryptophan levels of plasma isolated from peripheral blood decreased after therapy, but rebounded by the next day. The enzyme depletion column reduces circulating plasma tryptophan levels, and its use is well tolerated by patients. However, further development of this method will require study of the effects of diet and of the duration, interval, and frequency of use of this column on therapeutic efficacy. Problems include difficulties with extended diet compliance and apparently intensive mobilization of tryptophan from body stores, which may preclude the clinical application of this enzyme depletion column.

Liquid Phase Enzyme Reactor, a New Bioreactor Principle

One of the drawbacks of solid phase enzyme reactors is the sharp decrease in substrate affinity as shown by an increase in the Km app value. To circumvent this problem a liquid phase enzyme reactor system was designed. Biotin labeled L-Tryptophan side chain oxidase (TSO) was directly injected into the plasma circuit of a filter plasmaphoresis system of rabbits and adsorbed onto an Avidin column prior to its reentry into the animal's general blood circulation. In five experiments total L-Tryptophan depletion could be observed in the plasma circuit during 60 minutes of the experiment with complete readsorption of the enzyme to the Avidin column.

Hypothermia induced in mice by enzyme-mediated depletion of serotonin

Injection of a purified serotonin (and tryptophan)-degrading enzyme into mice produced a pronounced hypothermia when the mice were maintained at 22 degrees C, but not at 30 degrees C. Brain levels of serotonin and tryptophan were strikingly depleted, but concentrations of norepinephrine and dopamine remained unchanged.

Purification of indolyl-3-alkane alpha-hydroxylase by affinity chromatography on indolyl-agarose columns

Indolyl-3-alkane alpha-hydroxylase was isolated from soil isolate organism, Pseudomonas XA, by affinity chromatography on indolyl-agarose, using different indole derivatives (L-tryptophan, N-acetyl-L-tryptophan, indole-3-carboxaldehyde and 3-indole-acrylic acid). With the exception of N-acetyl-L-tryptophan-agarose, excellent yields were obtained. The affinity chromatography step caused a 15-fold increase in the specific activity of the enzyme. The purity of indolyl-3-alkane alpha-hydroxylase was comparable to the preparations obtained by conventional isolation techniques; however, it showed a 7- to 10-times higher overall yield. Affinity purified indolyl-3-alkane alpha-hydroxylase exhibited essentially one band in polyacrylamide gel electrophoresis and on isoelectric focusing.